As the Git FAQ [0] says:

> Git has a rename command git mv, but that is just for convenience. The effect is indistinguishable from removing the file and adding another with different name and the same content.

git diff, merge, and related tools have heuristics for detecting file moves (off by default, turned on with e.g. git diff -M) but they tend to break if a file is both moved and modified in the same commit.

[0] https://git.wiki.kernel.org/index.php/GitFaq#Why_does_Git_no...