I've written a bash script called git_diff_parent which, when passed a commit handle, performs git diff commit~1 commit; in other words, it diffs with its ancestor without having to specify commit~1 on the command line. I do this by parsing the git command line, finding which argument is the commit string (using git cat-file -t), replacing it with commit~1 commit then passing the new argument list to git diff. I've aliased this script in /etc/gitconfig so I can execute this command as git diff-parent:
[alias]
diff-parent = !git_diff_parent
This almost works except when I try to diff an individual file from a place other than the top-level repository directory, e.g.:
% pwd
/home/myhome/github/my-branch/rtl
% git diff-parent branch -- mycode.sv
<no output>
% git diff-parent branch -- rtl/mycode.sv
<diff output appears>
To debug this, I added pwd to my script to see the script's working directory. Lo and behold, it always launches from the top-level directory (/home/myhome/github/my-branch) rather than the subdirectory I'm in. I've even tried git -C . diff-parent ... to no avail.
So is there any way to make my alias launch from the current working directory?
https://git-scm.com/docs/git-config#Documentation/git-config.txt-alias
Note that shell commands will be executed from the top-level directory of a repository, which may not necessarily be the current directory.
GIT_PREFIXis set … from the original current directory.
(Emphasize and cut are mine — phd)
So you can do cd $GIT_PREFIX in git_diff_parent shell script.