tests: add test for unqualified include of a built-in template map
The feature was added in
081b08e4ea13 (templater: look for mapfiles in
template paths, 2015-05-15), but no test case was added.
Differential Revision: https://phab.mercurial-scm.org/D8797
commitctx: extract _filecommit too
This function is exclusively used in `commitctx`. So we should extract it too
for consistency and to reduce the `localrepo` bloat.
This is part of a larger refactoring/cleanup of the commitctx code to clarify
and augment the logic gathering metadata useful for copy tracing. The current
code is a tad too long and entangled to make such update easy.
Differential Revision: https://phab.mercurial-scm.org/D8710