Extdiff extension

This extension is currently being distributed along with Mercurial.

Author: Vadim Gelfer


The extdiff Mercurial extension allows you to use external programs to compare revisions, or revision with working dir. The external diff programs are called with a configurable set of options and two non-option arguments: paths to directories containing snapshots of files to compare, or paths to the files themselves if only one file is modified.


To enable this extension (in ~/.hgrc):

  extdiff =

Then, the extdiff command should be available:

$ hg extdiff -h
hg extdiff [OPT]... [FILE]...

use external program to diff repository (or selected files)

    Show differences between revisions for the specified files, using
    an external program.  The default program used is diff, with
    default options "-Npru".


You can run extdiff with default settings (diff -Npru):

$ hg extdiff
making snapshot of 1 files from rev dfe87137ed14
making snapshot of 1 files from working dir
diff -Npru crew.dfe87137ed14/mercurial/localrepo.py crew/mercurial/localrepo.py
--- crew.dfe87137ed14/mercurial/localrepo.py    2007-01-18 16:04:59.795697215 -0600
+++ crew/mercurial/localrepo.py 2007-01-18 16:04:59.805704181 -0600
@@ -990,10 +990,12 @@ class localrepository(repo.repository):

Or, use the -p option specify an external diff utility for comparing files:

$ hg extdiff -p kdiff3

Please note that the external diff utility of your choice must be able to compare directories.

You may use the -o option to specify options to the external diff utility:

$ hg extdiff -p diff -o -Npruw

You may also use --rev/-r and -I/-X options, as well as the list of file or directory names like normal hg diff command. The extdiff extension makes snapshots of only needed files, so running the external diff program will actually be pretty fast (at least faster than having to compare the entire tree).

Create Custom extdiff Commands

The extdiff extension also allows users to configure new diff commands in the hgrc files, so you do not need to type hg extdiff -p kdiff3 always.

  # add new command that runs GNU diff(1) in 'context diff' mode
  cmd.cdiff = gdiff
  opts.cdiff = -Nprc5

  # similarly, a command that runs GNU diff(1) in 'side-by-side' mode
  cmd.ydiff = gdiff
  opts.ydiff = -Npry

  # add new command called vdiff, runs kdiff3
  cmd.vdiff = kdiff3

  # add new command called meld, runs meld (no need to name twice)
  cmd.meld =

  # add new command called vimdiff, runs gvimdiff with DirDiff plugin
  #(see http://www.vim.org/scripts/script.php?script_id=102)
  # Non english user, be sure to put "let g:DirDiffDynamicDiffText = 1" in
  # your .vimrc
  cmd.vimdiff = gvim
  opts.vimdiff = -f '+next' '+execute "DirDiff" fnameescape(argv(0)) fnameescape(argv(1))'

  # add new command called ediff, runs emacs diff
  cmd.ediff = sh
  opts.ediff = -c 'if [ -d $0 ]; then emacs --eval "(ediff-directories \"$0\" \"$1\" \"\")"; else emacs --eval "(ediff-files \"$0\" \"$1\")"; fi'

  # add new command to run ImageMagick compare (image diff).  Does not work on directories.

  # note:  could subsitute ImageMagick's "display" call instead of "gqview" for
  # greater portability, but gqview is nicer

  cmd.imdiff = sh  
  opts.imdiff = -c 'compare $0 $1 compared.png; gqview compared.png'

Each custom diff commands can have two parts: a 'cmd' and an 'opts' part. The cmd.xxx option defines the name of an executable program that will be run, and opts.xxx defines a set of command-line options which will be inserted to the command between the program name and the files/directories to diff (i.e. the cdiff example above).

With the sample configuration above, you may now invoke the new commands:

$ hg vdiff    # call kdiff3
$ hg cdiff    # call gdiff with -Nprc5 option
$ hg meld     # call meld
$ hg ediff    # call emacs diff
$ hg imdiff   # call compare for an image diff  (don't invoke on directories)

FileMerge on Mac OS X

To use FileMerge with extdiff on Mac OS X, create the following shell script called opendiff-w somewhere in your $PATH (remember to make the script executable: chmod a+x opendiff-w):

# opendiff returns immediately, without waiting for FileMerge to exit.
# Piping the output makes opendiff wait for FileMerge.
opendiff "$@" | cat

Add to your .hgrc:

cmd.opendiff = opendiff-w

You can now use FileMerge for diffing from Mercurial:

$ hg opendiff

See also


ExtdiffExtension (last edited 2020-01-23 22:11:51 by JonathanPlona)