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

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:

#!/bin/sh -x

# Fill in your git.git working tree path here: GIT_GIT_REPO=

if [ -z "$GIT_GIT_REPO" ]; then
    echo Fill in GIT_GIT_REPO
    exit 1
fi

git init mv-test cd mv-test/

# Pick two sample files of non-trivial size, since files that are too small # never get tracked as moves. cp ${GIT_GIT_REPO}/Documentation/asciidoc.conf . cp ${GIT_GIT_REPO}/Documentation/blame-options.txt . git add * git commit -m "Start with two files from git.git/Documentation"

# Now rename them to something. Using 1 & 2 because they're nice & short. git mv asciidoc.conf 1 git mv blame-options.txt 2

# Status sees the rename git status

# So does the summary on the commit git commit -m "Rename both files"

# And move tracking works git diff -M --stat --summary HEAD~.. git diff -C --stat --summary HEAD~..

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

# Status knows what's going on git status

# So does commit 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~..

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

# Status gets it git status

# Commit understands git commit -m "Swap 2 & 3"

# Diff has no idea git diff -M --stat --summary HEAD~.. git diff -C --stat --summary HEAD~..

---

At first, I thought it was because the "git mv" command recorded something in the index that's lost once the commit happens.

To check if that was so, I went back to the commit in question, did a "git reset HEAD~1" and "git add -A ." and git status understood what was going on just fine.