The error message 'Both master and main branch not found!' is misleading when the actual logic checks for remote branches beyond just master/main (via remote_branch). Update the message to reflect that no suitable base branch was found, not just that master/main are missing.

The shell script for the rbm alias is quite complex and has a confusing order of precedence for branch detection. It could be simplified for better readability and maintainability, while also making the logic more intuitive.

The current logic prioritizes a local master or main branch over the remote's default branch if the default branch is named something other than master or main (e.g., develop). This seems to contradict the goal of detecting the base branch from origin/HEAD first.

Here's a simplified version that has a clearer order of precedence:

1. Check origin/HEAD for the default branch. Prefer a local tracking branch if it exists, otherwise use the remote branch.
2. If not found, fall back to checking for a local master branch.
3. If still not found, fall back to checking for a local main branch.
4. If no branch is found, print an error.

This revised script is shorter, easier to understand, and more robustly follows the intended logic of prioritizing the remote's default branch. I've also updated the error message to be more accurate.

!fn(){ base=''; remote_head=$(git symbolic-ref --quiet --short refs/remotes/origin/HEAD 2>/dev/null || true); if [ -n "$remote_head" ]; then remote_branch=${remote_head#origin/}; if [ "$remote_branch" != "$remote_head" ]; then if git show-ref --verify --quiet "refs/heads/$remote_branch"; then base=$remote_branch; elif git show-ref --verify --quiet "refs/remotes/$remote_head"; then base=$remote_head; fi; fi; fi; if [ -z "$base" ]; then if git show-ref --verify --quiet refs/heads/master; then base=master; elif git show-ref --verify --quiet refs/heads/main; then base=main; fi; fi; if [ -z "$base" ]; then echo 'Could not determine default branch (main, master, or from origin/HEAD).' >&2; return 1; fi; git rebase "$base" "$@"; };fn

Preserve rebase options before inserting base branch

The alias now forwards "$@" to git rebase but it prepends the resolved base as the first argument. Git parses options before positional arguments, so running git rbm --autostash or git rbm -i executes git rebase main --autostash, which treats --autostash as a branch name and aborts with fatal: invalid refname. This fails to deliver the stated goal of mirroring git rebase behaviour and breaks any use of the alias with rebase options. The base branch needs to be appended after user options (e.g. git rebase "$@" "$base") to keep flags working.

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⚠️ Potential issue | 🟠 Major

Respect origin/HEAD before falling back to local master

Line 34: when origin/HEAD points to a branch that isn’t master or main (e.g. trunk), but a stale local master branch still exists, we never reach the remote default fallback—the refs/heads/master check triggers first and forces every git rbm to rebase onto master. This regresses the very case this change set is meant to handle: repositories that renamed their default branch but kept master around. To reproduce, set origin/HEAD to origin/trunk, keep a local master, and run git rbm; it rebases onto master instead of origin/trunk.

Please move the generic remote_branch fallback ahead of the local master/main checks so we always honor the true default branch before considering legacy names.

-	rbm = "!fn(){ base=''; remote_head=$(git symbolic-ref --quiet --short refs/remotes/origin/HEAD 2>/dev/null || true); remote_branch=${remote_head#origin/}; if [ -n \"$remote_branch\" ] && [ \"$remote_branch\" != \"$remote_head\" ]; then case \"$remote_branch\" in master|main) if git show-ref --verify --quiet \"refs/heads/$remote_branch\"; then base=$remote_branch; elif git show-ref --verify --quiet \"refs/remotes/origin/$remote_branch\"; then base=origin/$remote_branch; fi;; esac; fi; if [ -z \"$base\" ] && git show-ref --verify --quiet refs/heads/master; then base=master; elif [ -z \"$base\" ] && git show-ref --verify --quiet refs/heads/main; then base=main; fi; if [ -z \"$base\" ] && [ -n \"$remote_branch\" ]; then if git show-ref --verify --quiet \"refs/heads/$remote_branch\"; then base=$remote_branch; elif [ -n \"$remote_head\" ] && git show-ref --verify --quiet \"refs/remotes/$remote_head\"; then base=$remote_head; fi; fi; if [ -z \"$base\" ]; then echo 'Both master and main branch not found!' >&2; return 1; fi; git rebase \"$base\" \"$@\"; };fn"
+	rbm = "!fn(){ base=''; remote_head=$(git symbolic-ref --quiet --short refs/remotes/origin/HEAD 2>/dev/null || true); remote_branch=${remote_head#origin/}; if [ -n \"$remote_branch\" ] && [ \"$remote_branch\" != \"$remote_head\" ]; then case \"$remote_branch\" in master|main) if git show-ref --verify --quiet \"refs/heads/$remote_branch\"; then base=$remote_branch; elif git show-ref --verify --quiet \"refs/remotes/origin/$remote_branch\"; then base=origin/$remote_branch; fi;; esac; fi; if [ -z \"$base\" ] && [ -n \"$remote_branch\" ]; then if git show-ref --verify --quiet \"refs/heads/$remote_branch\"; then base=$remote_branch; elif [ -n \"$remote_head\" ] && git show-ref --verify --quiet \"refs/remotes/$remote_head\"; then base=$remote_head; fi; fi; if [ -z \"$base\" ] && git show-ref --verify --quiet refs/heads/master; then base=master; elif [ -z \"$base\" ] && git show-ref --verify --quiet refs/heads/main; then base=main; fi; if [ -z \"$base\" ]; then echo 'Both master and main branch not found!' >&2; return 1; fi; git rebase \"$base\" \"$@\"; };fn"