How to search Git commit messages (not diffs) in a software repository with regular expression and output those messages & their line number to a text file?
You can 'grep' through commit log messages by doing the following:
git log -E --grep="regex" --oneline >/tmp/results.txt
This will result in e.g.:
abcd1234 First commit containing regex word. defg5679 Another commit: regex is found here.
I'm not sure what you mean by line number - if you just want every line in the file numbered, you can achieve this by piping the results through nl:
git log -E --grep "foo" | nl -w 1 -s ' ' > /tmp/results.txt
(-w 1 left-aligns numbers, and -s ' ' puts a single space after the number before the text).