zsh:alias:git-base-branch: Make regexs more robust

Fixes (in order of the patterns that were touched):

- Only match `*` that come between BOL and the branch name in brackets,
  as another branch could be checked out at a commit containing a `*`

- Only throw out commits that were committed on our current branch and
  not those that contain the branch name in the message (e.g. `test`).

- Only match until first bracket as the commit message could also
  contain a pattern like `[.*]` that would be matched instead.

.config/zsh/zshrc.d/30-alias.zsh

@@ -34,10 +34,10 @@
 	alias gss='git stash'
 	# https://nilansanjaya.wordpress.com/2017/06/02/git-find-base-branch/
 	git_bb='git show-branch -a 2>/dev/null'
-	git_bb+=' | grep "\*"'
+	git_bb+=' | grep "^[^[]*\*"'
-	git_bb+=' | grep -v "$(git rev-parse --abbrev-ref HEAD)"'
+	git_bb+=' | grep -v "^[^[]*\[$(git rev-parse --abbrev-ref HEAD)\]"'
 	git_bb+=' | head -n1'
-	git_bb+=' | sed -E "s/^.*\[([^^~\]*)([~^].*)?\].*$/\1/"'
+	git_bb+=' | sed -E "s/^[^[]*\[([^]~^]*).*$/\1/"'
 	alias git-base-branch="$git_bb"
 	unset git_bb
 	# https://stackoverflow.com/a/1549155