While trying to troubleshoot what I’d done to mess up the Mercurial repositories managing my Drupal installations last weekend, I really would have liked a way to see what files had changes in specific revisions. Each revision to a Mercurial repository affects some files, of course, but it seems awfully hard to figure what files changed in that check-in.
I have since found a way to do that by customizing the output of Mercurial. To customize output, you can create templates on the command line (with —template) or for more powerful reformatting, create an output style file.
I struggled for a while to figure out how to use style files, and eventually came up with something that works for me so far.
Since I’ve installed Mercurial from Lee Cantey’s standard binary package for Mac OS X Leopard, I created the file “map-cmdline.changedfiles” at the “/Library/Python/2.5/site-packages/mercurial/templates” path. (Where you put the file may vary depending on where Mercurial is installed, and I’m sorry but I don’t know where it gets installed on other systems.) The contents of “map-cmdline.changedfiles” are below, along with my possibly inept description of what each line is doing:
# Get all of the files in the selected revision
# and stringify them, whatever that means
# but do not 'tabindent' or wrap them to 68/76 columns
# Without first setting changeset to the list of files
# you won't get output from subsequent lines
changeset = '{files|stringify}'
# List modified files, one per line
# preceded by M to mimic `hg status`
file = 'M {file}\n'
last_file = 'M {file}\n'
# List added files, one per line
# preceded by A to mimic `hg status`
file_add = 'A {file_add}\n'
last_file_add = 'A {file_add}\n'
# List deleted files, one per line
# preceded by ! to mimic `hg status`
file_del = '! {file_del}\n'
last_file_del = '! {file_del}\n'
I don’t know why the “map-cmdline.” portion of the filename is there, but as long as I have it, I can call the style file from the command line with what follows the period. So, I can call the style with “—style changedfiles” — and that tiny bit of voodoo seems reasonable enough to me. (The other styles in the directory above, many of which end in “.tmpl” extensions, seem related to the Mercurial Web server, hgweb. I tried, but I couldn’t use their names at the command line, with or without their extensions. Plus, their contents looked HTML-ish.)
With the “map-cmdline.changedfiles” style file saved in that location, I can call Mercurial’s “log” command:
$ hg log --style changedfiles -r tip
… which gives me a list of the files changed in the “tip” (or latest revision) of the repository. I could substitute in any revision identifier for “tip.”
I haven’t actually seen the “file_add” and “file_del” keywords in action; every time I’ve used this style file in the manner described, I’ve only seen files marked as “M” — even if I’m looking at a revision where new files were first checked into the repo. I’m confused by that, but I’m not going to let it sour my day at this point.
There might have been an easier way to do this but I didn’t find one last weekend. It took me some time to figure even this bit out, and I hope writing this post saves someone new to Mercurial from future frustration.