let got_patch own fileindex_path and call got_worktree_patch_complete only if got_wokrtree_patch_prepare hasn't failed. suggested by stsp@

Instead of flushing the fileindex after every patch in the patchfile just reuse the same fileindex and sync it only at the end of the patch operation. This speeds up 'got patch' on large repositories by quite a lot.

ok op

add a flag to got_patch to reverse a patch before applying and the -R flag for `got patch'. ok stsp@

as a cheap optimization got-read-patch was sending only the "\ No newline at end of file" lines that follows an addition (a "+" line). To be able to reverse patches in the future got_patch needs to know about all of these lines instead. No functional changes intended. ok stsp@

this allow to apply patches from subdirectories of the work tree root. Prodded by naddy@, ok stsp@.

Move some bits from the libexec helper to the main process so we know if the patch was generated by git or not and finally document the automatic stripping of a/ and b/ prefixes added by git-diff(1). ok stsp@

check_file_status used got_worktree_status to check if the file was in an allowed state, but it's wrong since the callback is not invoked on unchanged files. While here also fix a relate bug: unlink(newpath) is in the wrong spot and ends up removing files even when it shouldn't, so move it early in the got_worktree_schedule_* error handling. Finally, update the appropriate test case. It was passing before because got_worktree_schedule_add returned GOT_ERR_FILE_STATUS, not because check_file_status failed. ok stsp@

Augment got_patch_progress_cb by providing the hunks that were applied with offset (or that failed) and the recoverable error encountered during the operation (bad status, missing file, ...) got_patch now proceeds when a file fails to be patched and exits with GOT_ERR_PATCH_FAILED if no other errors are encountered. While here, also add a test for the 'hunk applied with offset' case and shrink test_patch_dont_apply and illegal_status by taking advantage that 'got patch' doesn't stop at the first error. (And add some other cases to illegal_status too.) discussed with and ok stsp@