Backport #14804
* CutDiffAroundLine makes the incorrect assumption that `---` and `+++` always represent part of the header of a diff.
This PR adds a flag to its parsing to prevent this problem and adds a streaming parsing technique to CutDiffAroundLine using an io.pipe instead of just sending data to an unbounded buffer.
Fix#14711
* Handle unquoted comment patch files
When making comment patches unfortunately the patch does not always quote the filename
This makes the diff --git header ambiguous again.
This PR finally adds handling for ambiguity in to parse patch
Fix#14812
* Add in testing for no error
There is no way currently for CutDiffAroundLine in this test to cause an
error however, it should still be tested.
Signed-off-by: Andrew Thornton <art27@cantab.net>
be25afc6de