Re: [BUG] Move tracking in git diff is not as good as in git status

From: Kyle J. McKay <mackyle@gmail.com>
Date: Feb 5, 2015, 07:39 UTC
Message-ID: <099A7D2D-6033-4A16-91DD-E2288BC5C729@gmail.com>
In-Reply-To: <20150205061142.GA31599@odin.ulthar.us>

On Feb 4, 2015, at 22:11, Scott Schmit wrote:

Show 12 quoted lines

> In my use of git, I've noticed that "git status" is a lot better at
> tracking moves and renames than "git diff", and this has recently  
> caused
> me a lot of headaches because a large number of moves were made in a
> single commit, and it was very difficult to figure out which moves  
> were
> right and which were wrong.
>
> I was using a fairly old version of git (1.7.11), but was able to
> reproduce it on git 2.2.1.
>
> Here's a reproduction recipe:

[...]

> # Now "shift" the files
> git mv 2 3
> git mv 1 2

[...]

Show 6 quoted lines

> git commit -m "2=1;3=2;"
>
> # Neither of these commands get it (but -C gets a glimmer of the  
> truth)
> git diff -M --stat --summary HEAD~..
> git diff -C --stat --summary HEAD~..

Ah, but did you try this:

   git diff -B -M --stat --summary HEAD~..

> # Swap the files in place
> git mv 3 tmp
> git mv 2 3
> git mv tmp 2

[...]

Show 5 quoted lines

> git commit -m "Swap 2 & 3"
>
> # Diff has no idea
> git diff -M --stat --summary HEAD~..
> git diff -C --stat --summary HEAD~..

Again, try this:

   git diff -B -M --stat --summary HEAD~..

You can even use this:

   git log -B -M --summary

to see them all.

While you can configure -M (or -C) to be on by default (see git config diff.renames), there does not appear to be a config option to turn on - B (--break-rewrites) by default.

And according to a recent thread [1], using -B and -M together can produce incorrect results so you might not want them both on by default anyway.

-Kyle

[1] http://thread.gmane.org/gmane.linux.kernel/1879635