Find commit with specific git note

Question

I use git notes in my repository. Sometimes I need to find a commit with note that includes given string. So far I was using this command:

git log --show-notes=* --grep="PATTERN" --format=format:%H

The problem here is that this prints every commit SHA with PATTERN, even if it's not in notes only in commit message. Is there a better way for that?

Answer 1

There is a placeholder for notes in the format string, %N. I don't know how to print the notes in one line, so I use a loop to test notes of all reachable commits one by one.

Try

git log --format=%H | while read commit;do
    git log -1 $commit --format=%N | if grep -q "PATTERN";then echo $commit;fi;
done

You can change echo $commit to git log -1 --show-notes $commit.

Answer 2

Notes are stored in a COMMITed TREE that's "hidden" off to the side under a notes ref (refs/notes/commits by default). That means you can process them just like content.

$ git grep Testing refs/notes/commits
refs/notes/commits:fad066950ba73c309e80451d0d0f706e45adf5a8:This is a test - Testing

$ git show fad0669
commit fad066950ba73c309e80451d0d0f706e45adf5a8
Author: Mark Adelsberger <adelsbergerm@xxx>
Date:   Thu Sep 6 07:51:15 2018 -0500

    1

Notes:
    This is a test - Testing

diff --git a/file1 b/file1
index e69de29..038d718 100644
--- a/file1
+++ b/file1
@@ -0,0 +1 @@
+testing

Answer 3

You could search each note and only output the corresponding commit if the search matches.

#!/usr/bin/env bash

git notes list | while read -r note_and_commit_raw;
do
    note_and_commit=($note_and_commit_raw)
    git cat-file -p "${note_and_commit[0]}" | grep --quiet 'search string' &&
        git --no-pager log  -1 --format=format:%H ${note_and_commit[1]}
done

Notes:

1. Use git log -1 (only output that commit) since it seems like you don’t want the ancestors of those commits
   • This is also the reason why I invoke git log for each commit
2. Use --notes instead of --show-notes since the latter is deprecated
3. Use of git --no-pager might be unnecessary with such a small format

Light analysis

I use Git Notes daily for my own manually-written notes. In other words there is no program that writes my notes, so I don’t end up with a huge amount of stuff to search through.

Apparently I only have 467 notes in refs/notes/commits. The command takes 1.220s to complete (probably with everything in disk cache etc.) if I provide a search string which matches none of the commits. So this might not really scale if you have a lot of notes.

A more efficient program could probably be implemented by using what Mark pointed out in his answer.