Understanding and modifying the default diff for commits

[Andres Sommerhoff]

Hi all, I want to intervene the diff operation used by the mercurial
commit. I want to collect only the meaningful changes a heavy directory
tree full of XML files (this to make easier to audit what really has
changed, but also saving some disk space by doing so doesn’t hurt). I was
looking in internet and some mercurial add that could help, put I was
unsuccessfully, so thinking to make my own extension (or maybe some
scripting in pre-commit hook).

I will appreciate any advice where to start my intervention of the diff
process during the commit of mercurial if I go to make my own extension?
Any help for locating the diff code that is used by mercurial (to look and
learn how is the interaction with it)?

If you are curious about the problem I’m trying to deal with it, it is the
software KNIME that the projects (scientific models) developed in that
software is saved in several XML files, where each XML represent a small
portion of the model (“nodes” as called in KNIME). One project can easily
have more than 500 nodes (-> XML files). If I change a single node and save
the project, then not only the single related file is changes but all the
500 XML files are also updated. Inside each XML file the “last modification
date” and “last author” is changed.

I’m looking to skip all the files that the single change was updating “last
modification date” and “last author” but nothing else. By doing so, I can
focus in the important changes, making easy to audit the manful
modifications, merges can be far less cumbersome, and the history much
cleaner when making a log on a specific file.

Maybe a simple command line option for the commit is the solution, but I
see no official option in the commit command in order to use an alternative
diff tool for calculating the patches. On the other hand, as far I read,
the “extdiff” option only affect the comparison of the revisions, but not
for commit process (maybe I’m wrong on this last sentence). Or maybe a
commit command line using the function “diff([includepattern [,
excludepattern]]):” in conjunction with “--exclude “ will make the magic
I’m looking for, but I couldn’t figure it out yet.

I’m on Windows 10, using Mercurial and TortoiseHg 5.0.2.

Regards, Andres
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