convert: fix git copy file content conversions There was a bug in the git convert code where if you copied a file and modified the copy source in the same commit, and if the copy dest was alphabetically earlier than the copy source, the converted version would use the copy dest contents for both the source and the target. The root of the bug is that the git diff-tree output is formatted like so: :<mode> <mode> <oldhash> <newhash> <state> <src> <dest> :100644 100644 c1ab79a15... 3dfc779ab... C069 oldname newname :100644 100644 c1ab79a15... 03e2188a6... M oldname The old code would always take the 'oldname' field as the name of the file being processed, then it would try to do an extra convert for the newname. This works for renames because it does a delete for the oldname and a create for the newname. For copies though, it ends up associating the copied content (3dfc779ab above) with the oldname. It only happened when the dest was alphabetically before because that meant the copy got processed before the modification. The fix is the treat copy lines as affecting only the newname, and not marking the oldname as processed.