Backport #14624
GetCommit() assumes that all 40 char strings are SHA1s. This leads to an
error if you try to do a PR on a branch which is 40 characters long.
This PR attempts the SHA first - and if it fails will switch to using rev-parse.
Fix#14470
Signed-off-by: Andrew Thornton <art27@cantab.net>
This module is merged from https://github.com/go-gitea/git which is a Go module to access Git through shell commands. Now it's a part of gitea's main repository for easier pull request.