Find the nearest parent branch of the current git branch

who_is_my_mummy.sh

#!/usr/bin/env zsh

git show-branch -a \
| grep '\*' \
| grep -v `git rev-parse --abbrev-ref HEAD` \
| head -n1 \
| sed 's/.*\[\(.*\)\].*/\1/' \
| sed 's/[\^~].*//'

# How it works:
# 1| Display a textual history of all commits.
# 2| Ancestors of the current commit are indicated
#    by a star. Filter out everything else.
# 3| Ignore all the commits in the current branch.
# 4| The first result will be the nearest ancestor branch.
#    Ignore the other results.
# 5| Branch names are displayed [in brackets]. Ignore 
#    everything outside the brackets, and the brackets.
# 6| Sometimes the branch name will include a ~2 or ^1 to
#    indicate how many commits are between the referenced
#    commit and the branch tip. We don't care. Ignore them.

This does not return master branch name when master branch is the parent of the branch I check.

git log --decorate
| grep 'commit'
| grep 'origin/'
| head -n 2
| tail -n 1
| awk '{ print $2 }'
| tr -d "\n"

This seems to work for me. However I'm not totally gathering why it wouldn't show return the latest commit that has 'origin' in the first couple lines of the current branch 🤔 @verdverm

https://explainshell.com/explain?cmd=git+log+--decorate+%7C+grep+%27commit%27+%7C+grep+%27origin%2F%27+%7C+head+-n+2+%7C+tail+-n+1+%7C+awk+%27%7B+print+%242+%7D%27+%7C+tr+-d+%22%5Cn%22

@JackHowa we ended up recording the source branch at time of creation in a json file. This is exact and reliable. We have found many new and interesting uses for a "branch-config" (./bfg/*.json). Trying to figure it out from git was too troublesome.

that makes sense; we're leaning the same way. thanks @verdverm

@joechrysler It's not working for me on Windows 10, Could you please guide me?

Thanks!

In my case I see output as shown below, so all scripts above don't work correctly. Thus I enchanted a random script to show a correct branch. This is usually happening for me when I do cleanup and make many single-commit branches which I merge to the main one.

git show-branch -a \
| grep '\(\*\|^-.*\[\)' \
| grep -v '\['`git rev-parse --abbrev-ref HEAD`'\([\^]\|~\d\+\)\?\]' \
| head -n1 \
| sed 's/.*\[\([^\^~]*\).*\].*/\1/;'

What I enchanced:

1. first grep greps not only stas, but also the latest line
2. second grep eliminates only branches with exact name. Match also includes cases like ^ and ~1231.
   Pattern doesn't use advantage of -E for better compatibility between various systems and grep implementations.
3. few sed's at the end were collapsed into a single one, taking advantage of eagerness of * operator.

git show-branch outputs I have in my repositories:

$ git show-branch -a
! [main] test2
 * [t] test3
  ! [t2] test2
   ! [upstream/HEAD] Merge pull request #640 from repo/branch
    ! [upstream/main] Merge pull request #640 from repo/branch
-----
+     [main] test2
 *    [t] test3
 *    [t^] test2
 *    [t~2] test2
  +   [t2] test2
 *+   [t~3] test1
----- [upstream/HEAD] Merge pull request #640 from repo/branch
$ git show-branch   
! [main] test2
 ! [t] test3
  * [t2] test2
---
+   [main] test2
 +  [t] test3
 +  [t^] test2
 +  [t~2] test2
  * [t2] test2
 +* [t~3] test1
--- [main^] Merge pull request #640 from repo/branch

First, thank you for this gist -- it's exactly what I was looking for. I have two suggestions to improve it:

1. To account for a branch commit distance larger than 9, the final sed command should be:
   's/[\^~][[:digit]]*//'
2. The last two sed commands could be a done with a single sed invocation and two '-e' arguments, one for each command.