fix: initialize libgit2 in merge_file

[msuozzo]

merge_file called into libgit2 without crate::init(), so when it ran
before anything else had initialized the library, libgit2's placeholder
allocator failed every allocation and the merge returned an error with
no message.

[DanielEScherzer]

community review: I would suggest putting the initialization in MergeFileInput::new() instead, which will always be called before this can run, but might also help other code paths

View changes since this review

[msuozzo]

Thanks! I'd lean toward keeping it in merge_file to match the rest of the crate: crate::init() lives at the entry points that actually do libgit2 work, while constructors like MergeFileOptions::new() and MergeFileInput::new() just fill in structs via the *_init functions, which don't need the library initialized. MergeFileInput only gets used by merge_file anyway, so there aren't really other paths it'd cover.

[DanielEScherzer]

Makes sense, thanks for explaining

View changes since this review

[weihanglo]

Thanks for the review and the patch, folks!

View changes since this review