fix(branch): prevent git delete-merged-branches from deleting default branch (#1132)

[vaibhavmashal]

Summary

Fixes #1132

When running \git delete-merged-branches\ on a repository where the default/primary branch is \master\ (or when \origin/HEAD\ is set) from a non-default branch, \git_extra_default_branch\ previously fell back to \main\ (or whatever \init.defaultBranch\ was set to globally), which resulted in \master\ being treated as a merged branch and deleted.

Changes

• Updated \git_extra_default_branch()\ in \helper/git-extra-utility\ to:
  1. Respect \git config --get git-extras.default-branch`n 2. Inspect
     efs/remotes/origin/HEAD\ symbolic ref
  2. Inspect \git config --get init.defaultBranch`n 4. Check if \main\ exists locally or remotely
  3. Check if \master\ exists locally or remotely
  4. Fall back to \main`n- Updated \�in/git-delete-merged-branches, \�in/git-show-merged-branches, and \�in/git-show-unmerged-branches\ to explicitly protect the detected default branch as well as primary branches (\main, \master, \ runk, \svn).

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[hyperupcall]

Woah this diff is huge, perhaps there was a mistake in the history of the branch of this PR?

[vaibhavmashal]

Good catch @hyperupcall! My initial branch history had diverged from upstream. I've rebased directly onto \upstream/master\ — the PR diff is now clean with just the intended fix (+14 / -4 across \git-delete-merged-branches, \git-show-merged-branches, \git-show-unmerged-branches, and \git-extra-utility).

[spacewander]

Let's add test in https://github.com/tj/git-extras/tree/main/tests to cover the change

[spacewander]

This hurts repo uses own or other remote names. We should append it after the existing init_default_branch branch.

[spacewander]

Maybe we should use Igrep -Fvx with separate -e arguments to avoid regex char in the branch name, like release/foo+bar

[vaibhavmashal]

Added unit tests in \ ests/test_delete_merged_branches.py\ to cover \git delete-merged-branches, \git show-merged-branches, and \git show-unmerged-branches.

The tests verify that:

• Merged feature branches are properly deleted.
• The default branch (\master\ / \main) is protected and preserved.
• Unmerged feature branches remain intact.

Pushed in commit \ca67303.

[vaibhavmashal]

Hi @spacewander,

Thank you for the review and suggestions!

I have addressed all the feedback in commit 7eb6eed:

1. Remote vs local default branch resolution: Updated git_extra_default_branch() in helper/git-extra-utility so init.defaultBranch is evaluated before falling back to origin/HEAD.
2. Special characters in branch names: Updated bin/git-delete-merged-branches, bin/git-show-merged-branches, and bin/git-show-unmerged-branches to use grep -Fvx -e "$default_branch" -e "main" -e "master" -e "trunk" -e "svn" instead of regex matching. This prevents branch names with special characters (such as +, ., etc.) from breaking pattern matching.
3. Unit Tests: Added test coverage in tests/test_delete_merged_branches.py (including testing branch names containing regex characters like release/foo+bar), all passing cleanly.