Ian Obermiller

Part time hacker, full time dad.

Side-by-side diffs for Mercurial (hg) & icdiff revisited


A while back I told you how to get side-by-side diffs in Mercurial using icdiff. Turns out the author of icdiff has added the --recursive flag to make the tool accept directories and diff the contents of the files within. New setup instructions follow.

1. Install icdiff

Same as before: Download and install icdiff, making sure /usr/local/bin is in your $PATH.

2. Setup Mercurial

Next, lets configure Mercurial so that it knows about icdiff. We'll also set the default pager for all commands to less. Add the following to your ~/.hgrc.


# extdiff passes two directories to the diff command
# --recursive tells icdiff to treat the two params as directories
# and recursively diff their contents.
# -- line-numbers shows line numbers on both sides
opts.icdiff=--recursive --line-numbers

# Setting the variable LESS is like passing those options to less.
# In this case, -F (quit if fits on screen), and -R (pass through control chars,
# required for color output)
pager = LESS='FR' less
# Use pager for these commands only. Add any commands you use here.
attend = icdiff,diff,status,log

You can now replace diff in your Mercurial commands with icdiff, and it will do a side-by-side diff instead of inline.

3. Aliases (optional)

Finally, since hg icdiff is of course too long, add the following aliases to your ~/.bashrc or ~/.zshrc:

# side-by-side diffs for uncommitted files
alias ic='hg icdiff'

# diff all changes since the base revision, including uncommitted
# (from master if you are using bookmarks, for example)
alias ica='hg icdiff -r .^'

# diff the existing changes, excluding uncommitted
alias ice='hg icdiff --ch .'