checkout: don't revert file on ambiguous tracking branches#504

SyntevoAlex wants to merge 2 commits into

gitgitgadget:mastergitgitgadget/git:masterfrom

SyntevoAlex:#0207(git)_2c_prevent_ambiguous_checkoutSyntevoAlex/git:#0207(git)_2c_prevent_ambiguous_checkoutCopy head branch name to clipboard