Ediff provides a convenient way for simultaneous browsing through the differences between a pair (or a triple) of files or buffers (which are called `variants' for our purposes). The files being compared, file-A, file-B, and file-C (if applicable) are shown in separate windows (side by side, one above the another, or in separate frames), and the differences are highlighted as you step through them. You can also copy difference regions from one buffer to another (and recover old differences if you change your mind).
Another powerful feature is the ability to merge a pair of files into a third buffer. Merging with an ancestor file is also supported. Furthermore, Ediff is equipped with directory-level capabilities that allow the user to conveniently launch browsing or merging sessions on groups of files in two (or three) different directories.
In addition, Ediff can apply a patch to a file and then let you step though both files, the patched and the original one, simultaneously, difference-by-difference. You can even apply a patch right out of a mail buffer, i.e., patches received by mail don't even have to be saved. Since Ediff lets you copy differences between variants, you can, in effect, apply patches selectively (i.e., you can copy a difference region from `file.orig' to `file', thereby undoing any particular patch that you don't like).
Ediff even understands multi-file patches and can apply them interactively! (Ediff can recognize multi-file patches only if they are in the context format or GNU unified format. All other patches are treated as 1-file patches. Ediff is [hopefully] using the same algorithm as `patch' to determine which files need to be patched.)
Ediff is aware of version control, which lets you compare files with their older versions. Ediff also works with remote and compressed files, automatically ftp'ing them over and uncompressing them. See section Remote and Compressed Files, for details.
This package builds upon ideas borrowed from Emerge, and several of Ediff's functions are adaptations from Emerge. Although Ediff subsumes and greatly extends Emerge, much of the functionality in Ediff is influenced by Emerge. The architecture and the interface are, of course, drastically different.
Ediff can be invoked interactively using the following functions, which can be run either from the minibuffer or from the menu bar. In the menu bar, all Ediff's entry points belong to three submenus of the Tools menu: Compare, Merge, and Apply Patch.
ediff-files
ediff
ediff-buffers
ediff-files3
ediff3
ediff-buffers3
edirs
ediff-directories
edirs3
ediff-directories3
edir-revisions
ediff-directory-revisions
edir-merge-revisions
ediff-merge-directory-revisions
edir-merge-revisions-with-ancestor
ediff-merge-directory-revisions-with-ancestor
ediff-windows-wordwise
ediff-windows-linewise
ediff-regions-wordwise
ediff-regions-linewise
ediff-revision
ediff-patch-file
epatch
ediff-patch-file will actually use the `patch'
utility to change the the original files on disk. This is not that
dangerous, since you will always have the original contents of the file
saved in another file that has the extension `.orig'.
Furthermore, if the file is under version control, then you can always back
out to one of the previous versions (see the section on Version Countrol in
Emacs manual).
ediff-patch-file is careful about versions control: if the file
to be patched is checked in, then Ediff will offer to check it out, because
failing to do so may result in the loss of the changes when the file is
checked out the next time.
If you don't intend to modify the file via the patch and just want to see
what the patch is all about (and decide later), then
ediff-patch-buffer might be a better choice.
ediff-patch-buffer
epatch-buffer
ediff-patch-file for that (and when you want the original file to be
modified by the `patch' utility).
ediff-merge-files
ediff-merge
ediff-merge-files-with-ancestor
ediff-merge-with-ancestor
ediff-merge, but with a third ancestor file.
ediff-merge-buffers
ediff-merge-buffers-with-ancestor
edirs-merge
ediff-merge-directories
edirs-merge-with-ancestor
ediff-merge-directories-with-ancestor
ediff-merge-revisions
ediff-merge-revisions-with-ancestor
ediff-documentation
ediff-show-registry
eregistry
If you want Ediff to be loaded from the very beginning of your Emacs session, you should put this line in your `~/.emacs' file:
(require 'ediff)
Otherwise, Ediff will be loaded automatically when you use one of the above functions, either directly or through the menus.
When the above functions are invoked, the user is prompted for all the
necessary information--typically the files or buffers to compare, merge, or
patch. Ediff tries to be smart about these prompts. For instance, in
comparing/merging files, it will offer the visible buffers as defaults. In
prompting for files, if the user enters a directory, the previously input
file name will be appended to that directory. In addition, if the variable
ediff-use-last-dir is not nil, Ediff will offer
previously entered directories as defaults (which will be maintained
separately for each type of file, A, B, or C).
All the above functions use the POSIX diff or diff3 programs
to find differences between two files. They process the diff output
and display it in a convenient form. At present, Ediff understands only
the plain output from diff. Options such as `-c' are not supported,
nor is the format produced by incompatible file comparison programs such as
the VMS version of diff.
The functions ediff-files, ediff-buffers,
ediff-files3, ediff-buffers3 first display the coarse,
line-based difference regions, as reported by the `diff' program. The
total number of difference regions and the current difference number are
always displayed in the mode line of the control window.
Since diff may report fairly large chunks of text as being different,
even though the difference may be localized to just a few words or even
to the white space or line breaks, Ediff further refines the
regions to indicate which exact words differ. If the only difference is
in the white space and line breaks, Ediff says so.
On a color display, fine differences are highlighted with color; on a monochrome display, they are underlined. See section Highlighting Difference Regions, for information on how to customize this.
The functions ediff-windows-wordwise,
ediff-windows-linewise, ediff-regions-wordwise and
ediff-regions-linewise do comparison on parts of existing Emacs
buffers. Since ediff-windows-wordwise and
ediff-regions-wordwise are intended for relatively small segments
of buffers, comparison is done on the basis of words rather than lines.
No refinement is necessary in this case. These commands are recommended
only for relatively small regions (perhaps, up to 100 lines), because
these functions have a relatively slow startup.
To compare large regions, use ediff-regions-linewise. This
command displays differences much like ediff-files and
ediff-buffers.
The functions ediff-patch-file and ediff-patch-buffer apply a
patch to a file or a buffer and then run Ediff on the appropriate
files/buffers, displaying the difference regions.
The entry points ediff-directories, ediff-merge-directories,
etc., provide a convenient interface for comparing and merging files in
different directories. The user is presented with Dired-like interface from
which one can run a group of related Ediff sessions.
For files under version control, ediff-revision lets you compare
the file visited by the current buffer to one of its checked-in versions.
You can also compare two checked-in versions of the visited file.
Moreover, the functions ediff-directory-revisions,
ediff-merge-directory-revisions, etc., let you run a group of
related Ediff sessions by taking a directory and comparing (or merging)
versions of files in that directory.
All Ediff commands are displayed in a Quick Help window, unless you type ? to shrink the window to just one line. You can redisplay the help window by typing ? again. The Quick Help commands are detailed below.
Many Ediff commands take numeric prefix arguments. For instance, if you
type a number, say 3, and then j (ediff-jump-to-difference),
Ediff moves to the third difference region. Typing 3 and then a
(ediff-diff-to-diff) copies the 3d difference region from variant A
to variant B. Likewise, 4 followed by ra restores the 4th difference
region in buffer A (if it was previously written over via the command
a).
Some commands take negative prefix arguments as well. For instance, typing - and then j will make the last difference region current. Typing -2 then j makes the penultimate difference region current, etc.
Without the prefix argument, all commands operate on the currently selected difference region. You can make any difference region current using the various commands explained below.
For some commands, the actual value of the prefix argument is immaterial. However, if supplied, the prefix argument may modify the command (see ga, gb, and gc).
ediff-diff-program and ediff-diff-options). Without the
argument, it saves customized `diff' output (see
ediff-custom-diff-program and ediff-custom-diff-options), if
it is available.
ediff-auto-refine-limit. In this situation,
Ediff doesn't do automatic refinement in order to improve response time.
(Ediff doesn't auto-refine on dumb terminals as well, but * still
works there. However, the only useful piece of information it can tell you
is whether or not the difference regions disagree only in the amount of
white space.)
This command is also useful when the highlighted fine differences are
no longer current, due to user editing.
ediff-custom-diff-program on the variants and displays the
buffer containing the output. This is useful when you must send the output
to your Mom.
With a prefix argument, displays the plain `diff' output.
See section Patch and Diff Programs, for details.
ediff-windows-* and ediff-regions-*, which see.
ediff-merge-window-share, which see.
ediff-combine-diffs and ediff-combination-pattern.
The following commands can be invoked from within any Ediff session, although some of them are not bound to a key.
eregistry
ediff-show-registry
eregistry is an alias for ediff-show-registry.
See section Registry of Ediff Sessions, for more information on this registry.
ediff-toggle-multiframe
ediff-window-setup-function for details on how to make either of
these modes the default one.
This function can also be invoked from the Menubar. However, in some
cases, the change will take place only after you execute one of the Ediff
commands, such as going to the next difference or redisplaying.
ediff-revert-buffers-then-recompute-diffs
ediff-profile
ediff-profile toggles
profiling of ediff commands.
Ediff maintains a registry of all its invocations that are still active. This feature is very convenient for switching among active Ediff sessions or for quickly restarting a suspended Ediff session.
The focal point of this activity is a buffer called *Ediff Registry*. You can display this buffer by typing R in any Ediff Control Buffer or Session Group Buffer (see section Session Groups), or by typing M-x eregistry into the Minibuffer. The latter would be the fastest way to bring up the registry buffer if no control or group buffer is displayed in any of the visible Emacs windows. If you are in a habit of running multiple long Ediff sessions and often need to suspend, resume, or switch between them, it may be a good idea to have the registry buffer permanently displayed in a separate, dedicated window.
The registry buffer has several convenient key bindings. For instance, clicking mouse button 2 or typing RET or v over any session record resumes that session. Session records in the registry buffer provide a fairly complete description of each session, so it is usually easy to identify the right session to resume.
Other useful commands are bound to SPC (next registry record) and DEL (previous registry record). There are other commands as well, but you don't need to memorize them, since they are listed at the top of the registry buffer.
Several major entries of Ediff perform comparison and merging on
directories. On entering ediff-directories,
ediff-directories3,
ediff-merge-directories,
ediff-merge-directories-with-ancestor,
ediff-directory-revisions,
ediff-merge-directory-revisions, or
ediff-merge-directory-revisions-with-ancestor,
the user is presented with a
Dired-like buffer that lists files common to the directories involved along
with their sizes. (The list of common files can be further filtered through
a regular expression, which the user is prompted for.) We call this buffer
Session Group Panel because all Ediff sessions associated with the
listed files will have this buffer as a common focal point.
Clicking button 2 or typing RET or v over a record describing files invokes Ediff in the appropriate mode on these files. You can come back to the session group buffer associated with a particular invocation of Ediff by typing M in Ediff control buffer of that invocation.
Many commands are available in the session group buffer; some are applicable only to certain types of work. The relevant commands are always listed at the top of each session group buffer, so there is no need to memorize them.
In directory comparison or merging, a session group panel displays only the files common to all directories involved. The differences are kept in a separate buffer and are conveniently displayed by typing D to the corresponding session group panel. Thus, as an added benefit, Ediff can be used to compare the contents of up to three directories.
Session records in session group panels are also marked with +, for active sessions, and with -, for finished sessions.
Sometimes, it is convenient to exclude certain sessions from a group. Usually this happens when the user doesn't intend to run Ediff of certain files in the group, and the corresponding session records just add clutter to the session group buffer. To help alleviate this problem, the user can type h to mark a session as a candidate for exclusion and x to actually hide the marked sessions. There actions are reversible: with a prefix argument, h unmarks the session under the cursor, and x brings the hidden sessions into the view (x doesn't unmark them, though, so the user has to explicitly unmark the sessions of interest).
Group sessions also understand the command m, which marks sessions for future operations (other than hiding) on a group of sessions. At present, the only such group-level operation is the creation of a multi-file patch.
For group sessions created to merge files, Ediff can store all merges
automatically in a directory. The user is asked to specify such directory
if the value of ediff-autostore-merges is non-nil. If the value is
nil, nothing is done to the merge buffers--it will be the user's
responsibility to save them. If the value is t, the user will be
asked where to save the merge buffers in all merge jobs, even those that do
not originate from a session group. It the value is neither nil nor
t, the merge buffer is saved only if this merge session was
invoked from a session group. This behavior is implemented in the function
ediff-maybe-save-and-delete-merge, which is a hook in
ediff-quit-merge-hook. The user can supply a different hook, if
necessary.
The variable ediff-autostore-merges is buffer-local, so it can be
set in a per-buffer manner. Therefore, use setq-default to globally
change this variable.
A multi-file patch is a concatenated output of several runs of the Unix
`diff' command (some versions of `diff' let you create a
multi-file patch in just one run). Ediff facilitates creation of
multi-file patches as follows. If you are in a session group buffer
created in response to ediff-directories or
ediff-directory-revisions, you can mark (by typing m) the
desired Ediff sessions and then type P to create a
multi-file patch of those marked sessions.
Ediff will then display a buffer containing the patch.
The patch is generated by invoking `diff' on all marked individual
sessions (represented by files) and session groups (represented by
directories). Ediff will also recursively descend into any unmarked
session group and will search for marked sessions there. In this way, you
can create multi-file patches that span file subtrees that grow out of
any given directory.
In an ediff-directories session, it is enough to just mark the
requisite sessions. In ediff-directory-revisions revisions, the
marked sessions must also be active, or else Ediff will refuse to produce a
multi-file patch. This is because, in the latter-style sessions, there are
many ways to create diff output, and it is easier to handle by running
Ediff on the inactive sessions.
Last, but not least, by typing =, you can quickly find out which sessions have identical files, so you won't have to run Ediff on those sessions. This, however, works only on local, uncompressed files. For compressed or remote files, this command won't report anything.
Ediff works with remote, compressed, and encrypted files. Ediff supports `ange-ftp.el', `jka-compr.el', `uncompress.el' and `crypt++.el', but it may work with other similar packages as well. This means that you can compare files residing on another machine, or you can apply a patch to a file on another machine. Even the patch itself can be a remote file!
When patching compressed or remote files, Ediff does not rename the source
file (unlike what the patch utility would usually do). Instead, the
source file retains its name and the result of applying the patch is placed
in a temporary file that has the suffix `_patched' attached.
Generally, this applies to files that are handled using black magic, such
as special file handlers (ange-ftp and some compression and encryption
packages also use this method).
Regular files are treated by the patch utility in the usual manner,
i.e., the original is renamed into `source-name.orig' and the result
of the patch is placed into the file source-name (`_orig' is used
on systems like VMS, DOS, etc.)
Ediff has a rather self-explanatory interface, and in most cases you won't need to change anything. However, should the need arise, there are extensive facilities for changing the default behavior.
Most of the customization can be done by setting various variables in the `.emacs' file. Some customization (mostly window-related customization and faces) can be done by putting appropriate lines in `.Xdefaults', `.xrdb', or whatever X resource file is in use.
With respect to the latter, please note that the X resource for Ediff customization is `Ediff', not `emacs'. See section Window and Frame Configuration, See section Highlighting Difference Regions, for further details. Please also refer to Emacs manual for the information on how to set Emacs X resources.
The bulk of customization can be done via the following hooks:
ediff-load-hook
ediff-keymap-setup-hook
ediff-mode-map. These hooks are
run right after the default bindings are set but before
ediff-load-hook. The regular user needs not be concerned with this
hook--it is provided for implementors of other Emacs packages built on top
of Ediff.
ediff-before-setup-windows-hook
ediff-after-setup-windows-hook
ediff-suspend-hook
ediff-quit-hook
ediff-quit-hook holds one hook function,
ediff-cleanup-mess, which cleans after Ediff, as appropriate in
most cases. You probably won't want to change it, but you might
want to add other hook functions.
Keep in mind that hooks executing before ediff-cleanup-mess start
in ediff-control-buffer; they should also leave
ediff-control-buffer as the current buffer when they finish.
Hooks that are executed after ediff-cleanup-mess should expect
the current buffer be either buffer A or buffer B.
ediff-cleanup-mess doesn't kill the buffers being compared or
merged (see ediff-cleanup-hook, below).
ediff-cleanup-hook
ediff-quit-hook. This is a good
place to do various cleanups, such as deleting the variant buffers.
Ediff provides a function, ediff-janitor, as one such possible
hook, which you can add to ediff-cleanup-hook with
add-hooks.
This function kills buffers A, B, and, possibly, C, if these buffers aren't
modified. In merge jobs, buffer C is never deleted. However, the side
effect of using this function is that you may not be able to compare the
same buffer in two separate Ediff sessions: quitting one of them will
delete this buffer in another session as well.
ediff-quit-merge-hook
ediff-maybe-save-and-delete-merge, which is a function that attempts
to save the merge buffer according to the value of
ediff-autostore-merges, as described later.
ediff-before-setup-control-frame-hook
ediff-after-setup-control-frame-hook
ediff-control-buffer), which requires
special care in writing these hooks. Take a look at
ediff-default-suspend-hook and ediff-default-quit-hook to
see what's involved.
ediff-startup-hook
ediff-select-hook
ediff-unselect-hook
ediff-prepare-buffer-hook
ediff-display-help-hook
ediff-mode-hook
ediff-registry-setup-hook
ediff-session-group-setup-hook
ediff-quit-session-group-hook
ediff-meta-buffer-keymap-setup-hook
ediff-meta-buffer-map -- the
map that controls key bindings in the meta buffer. Since
ediff-meta-buffer-map is a local variable, you can set different
bindings for different kinds of meta buffers.
Ediff provides quick help using its control panel window. Since this window takes a fair share of the screen real estate, you can toggle it off by typing ?. The control window will then shrink to just one line and a mode line, displaying a short help message.
The variable ediff-use-long-help-message tells Ediff whether
you use the short message or the long one. By default, it
is set to nil, meaning that the short message is used.
Set this to t, if you want Ediff to use the long
message by default. This property can always be changed interactively, by
typing ? into Ediff Control Buffer.
If you want to change the appearance of the help message on a per-buffer
basis, you must use ediff-startup-hook to change the value of
the variable ediff-help-message, which is local to
ediff-control-buffer.
On a non-windowing display, Ediff sets things up in one frame, splitting it between a small control window and the windows for buffers A, B, and C. The split between these windows can be horizontal or vertical, which can be changed interactively by typing | while the cursor is in the control window.
On a window display, Ediff sets up a dedicated frame for Ediff Control
Panel and then it chooses windows as follows: If one of the buffers
is invisible, it is displayed in the currently selected frame. If
a buffer is visible, it is displayed in the frame where it is visible.
If, according to the above criteria, the two buffers fall into the same
frame, then so be it--the frame will be shared by the two. The same
algorithm works when you type C-l (ediff-recenter), p
(ediff-previous-difference), n
(ediff-next-difference), etc.
The above behavior also depends on whether the current frame is splittable, dedicated, etc. Unfortunately, the margin of this book is too narrow to present the details of this remarkable algorithm.
The upshot of all this is that you can compare buffers in one frame or in different frames. The former is done by default, while the latter can be achieved by arranging buffers A, B (and C, if applicable) to be seen in different frames. Ediff respects these arrangements, automatically adapting itself to the multi-frame mode.
Ediff uses the following variables to set up its control panel (a.k.a. control buffer, a.k.a. quick help window):
ediff-control-frame-parameters
ediff-control-frame-parameters directly. For instance, you can
specify in `~/.Xdefaults' the color of the control frame
using the resource `Ediff*background'.
In general, any X resource pertaining the control frame can be reached
via the prefix Ediff*.
ediff-control-frame-position-function
ediff-control-frame-position-function to an
appropriate function.
The default value of this variable is
ediff-make-frame-position. This function places the control frame in
the vicinity of the North-East corner of the frame displaying buffer A.
The following variables can be used to adjust the location produced by
ediff-make-frame-position and for related customization.
ediff-narrow-control-frame-leftward-shift
ediff-wide-control-frame-rightward-shift
ediff-control-frame-upward-shift
ediff-prefer-iconified-control-frame
t, the control frame becomes iconified
automatically when you toggle the quick help message off. This saves
valuable real estate on the screen. Toggling help back will deiconify
the control frame.
To start Ediff with an iconified Control Panel, you should set this
variable to t and ediff-prefer-long-help-message to
nil (see section Quick Help Customization). This behavior is useful
only if the window manager is TWM or a derivative.
To make more creative changes in the way Ediff sets up windows, you can
rewrite the function ediff-setup-windows. However, we believe
that detaching Ediff Control Panel from the rest and making it into a
separate frame offers an important opportunity by allowing you to
iconify that frame. The icon will usually accept all of the Ediff
commands, but will free up valuable real estate on your screen (this may
depend on your window manager, though).
The following variable controls how windows are set up:
ediff-window-setup-function
ediff-setup-windows-multiframe function, which is the default on
windowing displays. The plain setup, one where all windows are always
in one frame, is done by ediff-setup-windows-plain, which is the
default on a non-windowing display (or in an xterm window). In fact,
under Emacs, you can switch freely between these two setups by executing
the command ediff-toggle-multiframe using the Minibuffer of the
Menubar.
If you don't like any of these setups, write your own function. See the
documentation for ediff-window-setup-function for the basic
guidelines. However, writing window setups is not easy, so you should
first take a close look at ediff-setup-windows-plain and
ediff-setup-windows-multiframe.
You can run multiple Ediff sessions at once, by invoking Ediff several times without exiting previous Ediff sessions. Different sessions may even operate on the same pair of files.
Each session has its own Ediff Control Panel and all the regarding a particular session is local to the associated control panel buffer. You can switch between sessions by suspending one session and then switching to another control panel. (Different control panel buffers are distinguished by a numerical suffix, e.g., `Ediff Control Panel<3>'.)
Sometimes it is convenient to be able to step through only some difference regions, those that match certain regular expressions, and to ignore all others. On other occasions, you may want to ignore difference regions that match some regular expressions, and to look only at the rest.
The commands #f and #h let you do precisely this.
Typing #f lets you specify regular expressions that match difference regions you want to focus on. We shall call these regular expressions regexp-A, regexp-B and regexp-C. Ediff will then start stepping through only those difference regions where the region in buffer A matches regexp-A and/or the region in buffer B matches regexp-B, etc. Whether `and' or `or' will be used depends on how you respond to a question.
When scanning difference regions for the aforesaid regular expressions, Ediff narrows the buffers to those regions. This means that you can use the expressions \` and \' to tie search to the beginning or end of the difference regions.
On the other hand, typing #h lets you specify (hide) uninteresting
regions. That is, if a difference region in buffer A matches
regexp-A, the corresponding region in buffer B matches regexp-B
and (if applicable) buffer C's region matches regexp-C, then the
region will be ignored by the commands n/SPC
(ediff-next-difference) and p/DEL
(ediff-previous-difference) commands.
Typing #f and #h toggles selective browsing on and off.
Note that selective browsing affects only ediff-next-difference
and ediff-previous-difference, i.e., the commands
n/SPC and p/DEL. #f and #h do not
change the position of the point in the buffers. And you can still jump
directly (using j) to any numbered
difference.
Users can supply their own functions to specify how Ediff should do
selective browsing. To change the default Ediff function, add a function to
ediff-load-hook which will do the following assignments:
(setq ediff-hide-regexp-matches-function 'your-hide-function) (setq ediff-focus-on-regexp-matches-function 'your-focus-function)
Useful hint: To specify a regexp that matches everything, don't simply type RET in response to a prompt. Typing RET tells Ediff to accept the default value, which may not be what you want. Instead, you should enter something like ^ or $. These match every line.
You can use the status command, i, to find out whether selective browsing is currently in effect.
The regular expressions you specified are kept in the local variables
ediff-regexp-focus-A, ediff-regexp-focus-B,
ediff-regexp-focus-C, ediff-regexp-hide-A,
ediff-regexp-hide-B, ediff-regexp-hide-C. Their default value
is the empty string (i.e., nothing is hidden or focused on). To change the
default, set these variables in `.emacs' using setq-default.
In addition to the ability to ignore regions that match regular expressions, Ediff can be ordered to start skipping over certain "uninteresting" difference regions. This is controlled by the following variable:
ediff-ignore-similar-regions
t, causes Ediff to skip over "uninteresting" difference regions,
which are the regions where the variants differ only in the amount of the
white space and newlines. This feature can be toggled on/off interactively,
via the command ##.
Note: In order for this feature to work, auto-refining of difference regions must be on, since otherwise Ediff won't know if there are fine differences between regions. On devices where Emacs can display faces, auto-refining is a default, but it is not turned on by default on text-only terminals. In that case, you must explicitly turn auto-refining on (such as, by typing @).
Reassurance: If many such uninteresting regions appear in a row, Ediff may take a long time to skip over them because it has to compute fine differences of all intermediate regions. This delay does not indicate any problem.
The following variables control the way Ediff highlights difference regions:
ediff-before-flag-bol
ediff-after-flag-eol
ediff-before-flag-mol
ediff-after-flag-mol
ediff-current-diff-face-A
ediff-current-diff-face-B
ediff-current-diff-face-C
ediff-fine-diff-face-A
ediff-fine-diff-face-B
ediff-fine-diff-face-C
ediff-even-diff-face-A
ediff-even-diff-face-B
ediff-even-diff-face-C
ediff-odd-diff-face-A
ediff-odd-diff-face-B
ediff-odd-diff-face-C
ediff-force-faces
t to make sure that
Ediff uses faces to highlight differences.
ediff-highlight-all-diffs
ediff-highlight-all-diffs to nil. Type h to
restore highlighting for all differences.
Ediff lets you switch between the two modes of highlighting. That is,
you can switch interactively from highlighting using faces to
highlighting using string flags, and back. Of course, switching has
effect only under a windowing system. On a text-only terminal or in an
xterm window, the only available option is highlighting with strings.
If you want to change the default settings for ediff-force-faces and
ediff-highlight-all-diffs, you must do it before Ediff is
loaded.
You can also change the defaults for the faces used to highlight the difference regions. There are two ways to do this. The simplest and the preferred way is to use the customization widget accessible from the menubar. Ediff's customization group is located under "Tools", which in turn is under "Programming". The faces that are used to highlight difference regions are located in the "Highlighting" subgroup of the Ediff customization group.
The second, much more arcane, method to change default faces is to include some Lisp code in `~/.emacs'. For instance,
(setq ediff-current-diff-face-A
(copy-face 'bold-italic 'ediff-current-diff-face-A))
would use the pre-defined fase bold-italic to highlight the current
difference region in buffer A (this face is not a good choice, by the way).
If you are unhappy with just some of the aspects of the default
faces, you can modify them when Ediff is being loaded using
ediff-load-hook. For instance:
(add-hook 'ediff-load-hook
(function (lambda ()
(set-face-foreground
ediff-current-diff-face-B "blue")
(set-face-background
ediff-current-diff-face-B "red")
(make-face-italic
ediff-current-diff-face-B))))
Note: it is not recommended to use internal-get-face
when defining Ediff's faces, since this may cause problems when there
are several frames with different font sizes. Instead, use
copy-face or set/make-face-... as shown above.
If buffers being compared are narrowed at the time of invocation of
Ediff, ediff-buffers will preserve the narrowing range. However,
if ediff-files is invoked on the files visited by these buffers,
that would widen the buffers, since this command is defined to compare the
entire files.
Calling ediff-regions-linewise or ediff-windows-linewise, or
the corresponding `-wordwise' commands, narrows the variants to the
particular regions being compared. The original accessible ranges are
restored when you quit Ediff. During the command, you can toggle this
narrowing on and off with the % command.
These two variables control this narrowing behavior:
ediff-start-narrowed
t, Ediff narrows the display to the appropriate range when it
is invoked with an `ediff-regions...' or
`ediff-windows...' command. If nil, these commands do
not automatically narrow, but you can still toggle narrowing on and off
by typing %.
ediff-quit-widened
Ediff has variables to control the way fine differences are highlighted. This feature gives you control over the process of refinement. Note that refinement ignores spaces, tabs, and newlines.
ediff-auto-refine
ediff-auto-refine-limit
ediff-forward-word-function
ediff-diff-program. For the default forward word function (which is
ediff-forward-word), a word is a string consisting of letters,
`-', or `_'; a string of punctuation symbols; a string of digits,
or a string consisting of symbols that are neither space, nor a letter.
This default behavior is controlled by four variables: ediff-word-1,
..., ediff-word-4. See the on-line documentation for these variables
and for the function ediff-forward-word for an explanation of how to
modify these variables.
Sometimes, when a region has too many differences between the variants, highlighting of fine differences is inconvenient, especially on color displays. If that is the case, type * with a negative prefix argument. This unhighlights fine differences for the current region.
To unhighlight fine differences in all difference regions, use the command @. Repeated typing of this key cycles through three different states: auto-refining, no-auto-refining, and no-highlighting of fine differences.
This section describes variables that specify the programs to be used for applying patches and for computing the main difference regions (not the fine difference regions):
ediff-diff-program
ediff-diff3-program
ediff-diff-options
ediff-diff3-options
ediff-diff-options, it may be useful to specify options
such as `-w' that ignore certain kinds of changes. However,
Ediff does not let you use the option `-c', as it doesn't recognize this
format yet.
ediff-patch-program
ediff-patch-options, ediff-backup-specs, and
ediff-backup-extension as described below.
ediff-patch-options
ediff-patch-program.
Note: the `-b' and `-z' options should be specified in
`ediff-backup-specs', not in ediff-patch-options.
It is recommended to pass the `-f' option to the patch program, so it won't
ask questions. However, some implementations don't accept this option, in
which case the default value of this variable should be changed.
ediff-backup-extension
ediff-backup-specs is given.
ediff-backup-specs
ediff-custom-diff-program
ediff-custom-diff-options
diff
program, it partially makes up for this drawback by letting you save the
output from diff in your preferred format, which is specified via
the above two variables.
The output generated by ediff-custom-diff-program (which doesn't
even have to be a standard-style `diff'!) is not used by Ediff. It is
provided exclusively so that you can
refer to
it later, send it over email, etc. For instance, after reviewing the
differences, you may want to send context differences to a colleague.
Since Ediff ignores the `-c' option in
ediff-diff-program, you would have to run diff -c separately
just to produce the list of differences. Fortunately,
ediff-custom-diff-program and ediff-custom-diff-options
eliminate this nuisance by keeping a copy of a difference list in the
desired format in a buffer that can be displayed via the command D.
ediff-patch-default-directory
Warning: Ediff does not support the output format of VMS
diff. Instead, make sure you are using some implementation of POSIX
diff, such as gnudiff.
Ediff supports three-way comparison via the functions ediff-files3 and
ediff-buffers3. The interface is the same as for two-way comparison.
In three-way comparison and merging, Ediff reports if any two difference
regions are identical. For instance, if the current region in buffer A
is the same as the region in buffer C, then the mode line of buffer A will
display `[=diff(C)]' and the mode line of buffer C will display
`[=diff(A)]'.
Merging is done according to the following algorithm.
If a difference region in one of the buffers, say B, differs from the ancestor file while the region in the other buffer, A, doesn't, then the merge buffer, C, gets B's region. Similarly when buffer A's region differs from the ancestor and B's doesn't, A's region is used.
If both regions in buffers A and B differ from the ancestor file, Ediff
chooses the region according to the value of the variable
ediff-default-variant. If its value is default-A then A's
region is chosen. If it is default-B then B's region is chosen.
If it is combined then the region in buffer C will look like
this:
#ifdef NEW /* variant A */ difference region from buffer A #else /* variant B */ difference region from buffer B #endif /* NEW */
The actual strings that separate the regions copied from buffer A and B
are controlled by the variable ediff-combination-pattern. Its
value should be a list of three strings. The first is inserted before
the difference region of buffer A; the second string goes between the
regions; the third goes after region B, as shown in the above example.
In addition to the state of the difference, Ediff displays the state of the
merge for each region. If a difference came from buffer A by default
(because both regions A and B were different from the ancestor and
ediff-default-variant was set to default-A) then
`[=diff(A) default-A]' is displayed in the mode line. If the
difference in buffer C came, say, from buffer B because the difference
region in that buffer differs from the ancestor, but the region in buffer A
does not (if merging with an ancestor) then `[=diff(B) prefer-B]' is
displayed. The indicators default-A/B and prefer-A/B are inspired by
Emerge and have the same meaning.
Another indicator of the state of merge is `combined'. It appears with any difference region in buffer C that was obtained by combining the difference regions in buffers A and B as explained above.
In addition to the state of merge and state of difference indicators, while merging with an ancestor file or buffer, Ediff informs the user when the current difference region in the (normally invisible) ancestor buffer is empty via the AncestorEmpty indicator. This helps determine if the changes made to the original in variants A and B represent pure insertion or deletion of text: if the mode line shows AncestorEmpty and the corresponding region in buffers A or B is not empty, this means that new text was inserted. If this indicator is not present and the difference regions in buffers A or B are non-empty, this means that text was modified. Otherwise, the original text was deleted.
Although the ancestor buffer is normally invisible, Ediff maintains difference regions there and advances the current difference region accordingly. All highlighting of difference regions is provided in the ancestor buffer, except for the fine differences. Therefore, if desired, the user can put the ancestor buffer in a separate frame and watch it there. However, on a TTY, only one frame can be visible at any given time, and Ediff doesn't support any single-frame window configuration where all buffers, including the ancestor buffer, would be visible. However, the ancestor buffer can be displayed by typing / to the control window. (Type C-l to hide it again.)
Note that the state-of-difference indicators `=diff(A)' and `=diff(B)' above are not redundant, even in the presence of a state-of-merge indicator. In fact, the two serve different purposes.
For instance, if the mode line displays `=diff(B) prefer(B)' and you copy a difference region from buffer A to buffer C then `=diff(B)' will change to `diff-A' and the mode line will display `=diff(A) prefer-B'. This indicates that the difference region in buffer C is identical to that in buffer A, but originally buffer C's region came from buffer B. This is useful to know because you can recover the original difference region in buffer C by typing r.
Ediff never changes the state-of-merge indicator, except in response to the ! command (see below), in which case the indicator is lost. On the other hand, the state-of-difference indicator is changed automatically by the copying/recovery commands, a, b, r, +.
The ! command loses the information about origins of the regions
in the merge buffer (default-A, prefer-B, or combined). This is because
recomputing differences in this case means running diff3 on
buffers A, B, and the merge buffer, not on the ancestor buffer. (It
makes no sense to recompute differences using the ancestor file, since
in the merging mode Ediff assumes that you have not edited buffers A and
B, but that you may have edited buffer C, and these changes are to be
preserved.) Since some difference regions may disappear as a result of
editing buffer C and others may arise, there is generally no simple way
to tell where the various regions in the merge buffer came from.
In three-way comparison, Ediff tries to disregard regions that consist entirely of white space. For instance, if, say, the current region in buffer A consists of the white space only (or if it is empty), Ediff will not take it into account for the purpose of computing fine differences. The result is that Ediff can provide a better visual information regarding the actual fine differences in the non-white regions in buffers B and C. Moreover, if the regions in buffers B and C differ in the white space only, then a message to this effect will be displayed.
In the merge mode, the share of the split between window C (the window
displaying the merge-buffer) and the windows displaying buffers A and B
is controlled by the variable ediff-merge-window-share. Its
default value is 0.5. To make the merge-buffer window smaller, reduce
this amount.
We don't recommend increasing the size of the merge-window to more than
half the frame (i.e., to increase the value of
ediff-merge-window-share) to more than 0.5, since it would be
hard to see the contents of buffers A and B.
You can temporarily shrink the merge window to just one line by typing s. This change is temporary, until Ediff finds a reason to redraw the screen. Typing s again restores the original window size.
With a positive prefix argument, the s command will make the merge window slightly taller. This change is persistent. With `-' or with a negative prefix argument, the command s makes the merge window slightly shorter. This change also persistent.
Ediff lets you automatically ignore the regions where only one of the
buffers A and B disagrees with the ancestor. To do this, set the
variable ediff-show-clashes-only to non-nil.
You can toggle this feature interactively by typing $.
Note that this variable affects only the show next/previous difference commands. You can still jump directly to any difference region directly using the command j (with a prefix argument specifying the difference number).
The variable ediff-autostore-merges controls what happens to the
merge buffer when Ediff quits. If the value is nil, nothing is done
to the merge buffer--it will be the user's responsibility to save it.
If the value is t, the user will be asked where to save the buffer
and whether to delete it afterwards. It the value is neither nil nor
t, the merge buffer is saved only if this merge session was
invoked from a group of related Ediff session, such as those that result
from ediff-merge-directories,
ediff-merge-directory-revisions, etc.
See section Session Groups. This behavior is implemented in the function
ediff-maybe-save-and-delete-merge, which is a hook in
ediff-quit-merge-hook. The user can supply a different hook, if
necessary.
The variable ediff-autostore-merges is buffer-local, so it can be
set in a per-buffer manner. Therefore, use setq-default to globally
change this variable.
Ediff supports version control and lets you compare versions of files
visited by Emacs buffers via the function ediff-revision. This
feature is controlled by the following variables:
ediff-version-control-package
(setq ediff-version-control-package 'rcs)Apart from the standard `vc.el', Ediff supports three other interfaces to version control: `rcs.el', `pcl-cvs.el', and `generic-sc.el'. The package `rcs.el' is written by Sebastian Kremer <sk@thp.Uni-Koeln.DE> and is available as
`ftp.cs.buffalo.edu:pub/Emacs/rcs.tar.Z' `ftp.uni-koeln.de:/pub/gnu/emacs/rcs.tar.Z'
Ediff's interface to the above packages allows the user to compare the versions of the current buffer or to merge them (with or without an ancestor-version). These operations can also be performed on directories containing files under version control.
In case of `pcl-cvs.el', Ediff can also be invoked via the function
run-ediff-from-cvs-buffer---see the documentation string for this
function.
When Ediff is running, the mode line of `Ediff Control Panel' buffer shows the current difference number and the total number of difference regions in the two files.
The mode line of the buffers being compared displays the type of the
buffer (`A:', `B:', or `C:') and (usually) the file name.
Ediff tries to be intelligent in choosing the mode line buffer
identification. In particular, it works well with the
`uniquify.el' and `mode-line.el' packages (which improve on
the default way in which Emacs displays buffer identification). If you
don't like the way Ediff changes the mode line, you can use
ediff-prepare-buffer-hook to modify the mode line.
Here are a few other variables for customizing Ediff:
ediff-split-window-function
split-window-vertically, but you can set it to
split-window-horizontally, if you so wish.
Ediff also lets you switch from vertical to horizontal split and back
interactively.
Note that if Ediff detects that all the buffers it compares are displayed in
separate frames, it assumes that the user wants them to be so displayed
and stops splitting windows. Instead, it arranges for each buffer to
be displayed in a separate frame. You can switch to the one-frame mode
by hiding one of the buffers A/B/C.
You can also swap the windows where buffers are displayed by typing
~.
ediff-merge-split-window-function
ediff-split-window-function, but it defaults
to split-window-horizontally instead of
split-window-vertically.
ediff-make-wide-display-function
ediff-make-wide-display-function for details. It is also
recommended to look into the source of the default function
ediff-make-wide-display.
You can toggle wide/regular display by typing m. In the wide
display mode, buffers A, B (and C, when applicable) are displayed in a
single frame that is as wide as the entire workstation screen. This is
useful when files are compared side-by-side. By default, the display is
widened without changing its height.
ediff-use-last-dir
nil,
Ediff uses the default directory of the current buffer when it
prompts the user for file names. Otherwise, it will use the
directories it had previously used for files A, B, or C, respectively.
ediff-no-emacs-help-in-control-buffer
t, makes C-h
behave like the DEL key, i.e., it will move you back to the previous
difference rather than invoking help. This is useful when, in an xterm
window or a text-only terminal, the Backspace key is bound to C-h and is
positioned more conveniently than the DEL key.
ediff-toggle-read-only-function
ediff-make-buffers-readonly-at-startup nil
ediff-keep-variants
t, meaning that the buffers being compared or merged will
be preserved when Ediff quits. Setting this to nil causes Ediff to
offer the user a chance to delete these buffers (if they are not modified).
Supplying a prefix argument to the quit command (q) temporarily
reverses the meaning of this variable. This is convenient when the user
prefers one of the behaviors most of the time, but occasionally needs the
other behavior.
However, Ediff temporarily resets this variable to t if it is
invoked via one of the "buffer" jobs, such as ediff-buffers.
This is because it is all too easy to loose day's work otherwise.
Besides, in a "buffer" job, the variant buffers have already been loaded
prior to starting Ediff, so Ediff just preserves status quo here.
Using ediff-cleanup-hook, one can make Ediff delete the variants
unconditionally (e.g., by making ediff-janitor into one of these hooks).
ediff-grab-mouse
t. Normally, Ediff grabs mouse and puts it in its
control frame. This is useful since the user can be sure that when he
needs to type an Ediff command the focus will be in an appropriate Ediff's
frame. However, some users prefer to move the mouse by themselves. The
above variable, if set to maybe, will prevent Ediff from grabbing
the mouse in many situations, usually after commands that may take more
time than usual. In other situation, Ediff will continue grabbing the mouse
and putting it where it believes is appropriate. If the value is
nil, then mouse is entirely user's responsibility.
Try different settings and see which one is for you.
Some users need to customize Ediff in rather sophisticated ways, which
requires different defaults for different kinds of files (e.g., SGML,
etc.). Ediff supports this kind of customization in several ways. First,
most customization variables are buffer-local. Those that aren't are
usually accessible from within Ediff Control Panel, so one can make them
local to the panel by calling make-local-variable from within
ediff-startup-hook.
Second, the function ediff-setup accepts an optional sixth
argument which has the form ((var-name-1 . val-1)
(var-name-2 . val-2) ...). The function
ediff-setup sets the variables in the list to the respective
values, locally in the Ediff control buffer. This is an easy way to
throw in custom variables (which usually should be buffer-local) that
can then be tested in various hooks.
Make sure the variable ediff-job-name and ediff-word-mode are set
properly in this case, as some things in Ediff depend on this.
Finally, if you want custom-tailored help messages, you can set the
variables ediff-brief-help-message-function and
ediff-long-help-message-function
to functions that return help strings.
When customizing Ediff, some other variables are useful, although they are
not user-definable. They are local to the Ediff control buffer, so this
buffer must be current when you access these variables. The control buffer
is accessible via the variable ediff-control-buffer, which is also
local to that buffer. It is usually used for checking if the current buffer
is also the control buffer.
Other variables of interest are:
ediff-buffer-A
ediff-buffer-B
ediff-buffer-C
ediff-window-A
ediff-window-B
ediff-window-C
ediff-control-frame
Ediff was written by Michael Kifer <kifer@cs.sunysb.edu>. It was inspired by emerge.el written by Dale R. Worley <drw@math.mit.edu>. An idea due to Boris Goldowsky <boris@cs.rochester.edu> made it possible to highlight fine differences in Ediff buffers. Alastair Burt <burt@dfki.uni-kl.de> ported Ediff to XEmacs, Eric Freudenthal <freudent@jan.ultra.nyu.edu> made it work with VC, Marc Paquette <marcpa@cam.org> wrote the toolbar support package for Ediff, and Hrvoje Niksic <hniksic@srce.hr> adapted it to the Emacs customization package.
Many people provided help with bug reports, patches, and advice. Without them, Ediff would not be nearly as useful as it is today. Here is a full list of contributors (I hope I didn't miss anyone):
Steve Baur (steve@xemacs.org), Neal Becker (neal@ctd.comsat.com), E. Jay Berkenbilt (ejb@ql.org), Alastair Burt (burt@dfki.uni-kl.de), Paul Bibilo (peb@delcam.co.uk), Kevin Broadey (KevinB@bartley.demon.co.uk), Harald Boegeholz (hwb@machnix.mathematik.uni-stuttgart.de), Bradley A. Bosch (brad@lachman.com), Michael D. Carney (carney@ltx-tr.com), Jin S. Choi (jin@atype.com), Scott Cummings (cummings@adc.com), Albert Dvornik (bert@mit.edu), Eric Eide (eeide@asylum.cs.utah.edu), Paul Eggert (eggert@twinsun.com), Kevin Esler (esler@ch.hp.com), Robert Estes (estes@ece.ucdavis.edu), Jay Finger (jayf@microsoft.com), Xavier Fornari (xavier@europe.cma.fr), Eric Freudenthal (freudent@jan.ultra.nyu.edu), Job Ganzevoort (Job.Ganzevoort@cwi.nl), Boris Goldowsky (boris@cs.rochester.edu), Allan Gottlieb (gottlieb@allan.ultra.nyu.edu), Thorbjoern Hansen (thorbjoern.hansen@mchp.siemens.de), Xiaoli Huang (hxl@epic.com), Lars Magne Ingebrigtsen (larsi@ifi.uio.no), Larry Gouge (larry@itginc.com), Karl Heuer (kwzh@gnu.org), (irvine@lks.csi.com), (jaffe@chipmunk.cita.utoronto.ca), David Karr (dkarr@nmo.gtegsc.com), Norbert Kiesel (norbert@i3.informatik.rwth-aachen.de), Leigh L Klotz (klotz@adoc.xerox.com), Fritz Knabe (Fritz.Knabe@ecrc.de), Heinz Knutzen (hk@informatik.uni-kiel.d400.de), Andrew Koenig (ark@research.att.com), Ken Laprade (laprade@dw3f.ess.harris.com), Will C Lauer (wcl@cadre.com), Richard Levitte (levitte@e.kth.se), Mike Long (mike.long@analog.com), Martin Maechler (maechler@stat.math.ethz.ch), Simon Marshall (simon@gnu.org), Richard Mlynarik (mly@adoc.xerox.com), Chris Murphy (murphycm@sun.aston.ac.uk), Erik Naggum (erik@naggum.no), Eyvind Ness (Eyvind.Ness@hrp.no), Ray Nickson (nickson@cs.uq.oz.au), David Petchey (petchey_david@jpmorgan.com), Benjamin Pierce (benjamin.pierce@cl.cam.ac.uk), Tibor Polgar (tlp00@spg.amdahl.com), David Prince (dave0d@fegs.co.uk), Paul Raines (raines@slac.stanford.edu), Bill Richter (richter@math.nwu.edu), C.S. Roberson (roberson@aur.alcatel.com), Kevin Rodgers (kevin.rodgers@ihs.com), Sandy Rutherford (sandy@ibm550.sissa.it), Heribert Schuetz (schuetz@ecrc.de), Andy Scott (ascott@pcocd2.intel.com), Axel Seibert (axel@tumbolia.ppp.informatik.uni-muenchen.de), Scott O. Sherman (Scott.Sherman@mci.com), Richard Stallman (rms@gnu.org), Richard Stanton (stanton@haas.berkeley.edu), Ake Stenhoff (etxaksf@aom.ericsson.se), Stig (stig@hackvan.com), Peter Stout (Peter_Stout@cs.cmu.edu), Chuck Thompson (cthomp@cs.uiuc.edu), Ray Tomlinson (tomlinso@bbn.com), Raymond Toy (toy@rtp.ericsson.se), Jan Vroonhof (vroonhof@math.ethz.ch), Philippe Waroquiers (philippe.waroquiers@eurocontrol.be), Klaus Weber (gizmo@zork.north.de), Ben Wing (wing@666.com), Ilya Zakharevich (ilya@math.ohio-state.edu), Eli Zaretskii (eliz@is.elta.co.il)
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