patch: fix patch hunk/metdata synchronization (issue3384) Git patches are parsed in two phases: 1) extract metadata, 2) parse actual deltas and merge them with the previous metadata. We do this to avoid dependency issues like "modify a; copy a to b", where "b" must be copied from the unmodified "a". Issue3384 is caused by flaky code I wrote to synchronize the patch metadata with the emitted hunk: if (gitpatches and (gitpatches[-1][0] == afile or gitpatches[-1][1] == bfile)): gp = gitpatches.pop()[2] With a patch like: diff --git a/a b/c copy from a copy to c --- a/a +++ b/c @@ -1,1 +1,2 @@ a +a @@ -2,1 +2,2 @@ a +a diff --git a/a b/a --- a/a +++ b/a @@ -1,1 +1,2 @@ a +b the first hunk of the first block is matched with the metadata for the block "diff --git a/a b/c", then the second hunk of the first block is matched with the metadata of the second block "diff --git a/a b/a", because of the "or" in the code paste above. Turning the "or" into an "and" is not enough as we have to deal with /dev/null cases for each file. We I remove this broken piece of code: # copy/rename + modify should modify target, not source if gp.op in ('COPY', 'DELETE', 'RENAME', 'ADD') or gp.mode: afile = bfile because "afile = bfile" set "afile" to stuff like "b/file" instead of "a/file", and because this only happens for git patches, which afile/bfile are ignored anyway by applydiff(). v2: - Avoid a traceback on git metadata desynchronization