We've been sometimes using lo and sometimes using my slices package, and we need to pick one
for consistency. Lo is more extensive and better maintained so we're going with that.
My slices package was a superset of go's own slices package so in some places I've just used
the official one (the methods were just wrappers anyway).
I've also moved the remaining methods into the utils package.
This fixes the problem that patching would stop at the first file that has a
conflict. We always want to patch all files.
Also, it's faster for large patches, and the code is a little bit simpler too.
All callers in this file now use reverseOnGenerate=false and
keepOriginalHeader=true, so hard-code that in the call to ModifiedPatchForLines
and get rid of the parameters.
The loop is pointless for two reasons:
- git apply --3way has this fallback built in already. If it can't do a
three-way merge, it will fall back to applying the patch normally.
- However, the only situation where it does this is when it can't do a 3-way
merge at all because it can't find the necessary ancestor blob. This can only
happen if you transfer a patch between different repos that don't have the
same blobs available; we are applying the patch to the same repo that is was
just generated from, so a 3-way merge is always possible. (Now that we fixed
the bug in the previous commit, that is.)
But the retry loop is not only pointless, it was actually harmful, because when
a 3-way patch fails with a conflict, git will put conflict markers in the
patched file and then exit with a non-zero exit status. So the retry loop would
try to patch the already patched file again, and this almost certainly fails,
but with a cryptic error message such as "error: main.go: does not exist in
index".
There's no reason to have two different ways of applying patches for whole-file
patches and partial patches; use --reverse for both. Not only does this simplify
the code a bit, but it fixes an actual problem: when reverseOnGenerate and
keepOriginalHeader are both true, the generated patch header is broken (the two
blobs in the line `index 6d1959b..6dc5f84 100644` are swapped). Git fails to do
a proper three-way merge in that case, as it expects the first of the two blobs
to be the common ancestor.
It would be possible to fix this by extending ModifiedPatchForLines to swap the
two blobs in this case; but this would prevent us from concatenating all patches
and apply them in one go, which we are going to do later in the branch.
We are going to add one more flag in the next commit.
Note that we are not using the struct inside patch_manager.go; we keep passing
the individual flags there. The reason for this will become more obvious later
in this branch.
