If we configure checkouts as git-svn, we don't need this. However, not all automation needs git-svn checkouts.
<rdar://problem/73362104>
Created attachment 417888 [details] Patch
rs=me
Committed r271602: <https://trac.webkit.org/changeset/271602>
Just for future reference, this was to fix issue like: https://ews-build.webkit.org/#/builders/6/builds/37820 "webkitpy.common.system.executive.ScriptError: Can't find a branch to diff against. svn-remote.svn.fetch is not in the git config and refs/remotes/origin/master does not exist"