git+zsh: stop tab-completion producing branch deletes that fail

`git push origin --delete <TAB>` completes to `origin/foo`, but `origin/foo` is
a LOCAL remote-tracking name — the ref on the server is just `foo`. So the
command zsh completes for you is the one git rejects, and it rejects it with
"remote ref does not exist", which reads as "that branch is gone" rather than
"you named it wrong".

The second half is worse, because it makes the first half look intermittent:
without pruning, `git branch -r` and the completion keep offering branches that
were deleted on the server weeks ago. Then some completions fail because the
branch is genuinely gone and others fail because of the prefix, with identical
error text.

Two fixes, one per cause:

- `fetch.prune = true` globally, so stale remote-tracking refs are dropped on
  every fetch/pull and dead branches stop being offered at all.
- `grmb`, which takes either form, prunes first, and reports per-branch rather
  than aborting the batch. `grmb origin/foo` and `grmb foo` both work.

Named grmb rather than the more obvious gbd because oh-my-zsh's git plugin
already binds gbd to `git branch --delete`. Aliases resolve before functions,
so the collision would not have errored — it would have silently tried to
delete a LOCAL branch when the whole point is the remote one. Caught by
`type gbd` after installing; check any new g* helper the same way.

grmb deliberately does not wrap `git push` itself — intercepting a git
subcommand to rewrite its arguments is the kind of thing that works until it
silently does the wrong thing to a refspec someone meant literally.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

zsh/zshrc

@@ -34,6 +34,46 @@ SAVEHIST=10000
 setopt SHARE_HISTORY
 setopt HIST_IGNORE_DUPS
 
+# Delete remote branches without fighting tab-completion.
+#
+# `git push origin --delete <TAB>` completes to `origin/foo`, but `origin/foo`
+# is a LOCAL remote-tracking name — the ref on the server is just `foo`. So the
+# command zsh completes for you is the one git rejects, with "remote ref does
+# not exist", which reads like the branch is missing rather than misnamed.
+#
+# grmb takes either form. It fetches with --prune first so branches already
+# deleted on the server stop being offered at all (that is the other half of
+# this annoyance, and `fetch.prune = true` from dotfiles/git/install.sh makes it
+# automatic everywhere else).
+#
+# Named grmb, not gbd: oh-my-zsh's git plugin already binds gbd to
+# `git branch --delete`, aliases resolve before functions, and the collision
+# fails in the worst possible way — `gbd origin/foo` would quietly try to
+# delete a LOCAL branch instead of the remote one. Check with `type <name>`
+# before adding any g* helper here.
+#
+#   grmb origin/my-branch     # completed form, works
+#   grmb my-branch other      # bare form, several at once
+grmb() {
+  emulate -L zsh
+  local remote=origin b rc=0
+  if [ "$#" -eq 0 ]; then
+    print -u2 "grmb: usage: grmb <branch>... (origin/ prefix optional)"
+    return 2
+  fi
+  git fetch --prune --quiet "$remote" || return 1
+  for b in "$@"; do
+    b=${b#${remote}/}
+    if git push "$remote" --delete "$b"; then
+      print "deleted ${remote}/${b}"
+    else
+      print -u2 "grmb: could not delete ${b} (already gone? check: git ls-remote --heads ${remote})"
+      rc=1
+    fi
+  done
+  return $rc
+}
+
 # Per-machine customizations (secrets, keys, local overrides) live in
 # ~/.zshrc.local, which bootstrap never touches. See zsh/zshrc.local.example
 # for the variables modules look for. Loaded last so it can override anything.