Packed-refs v2 Part IV: abstract some parts of the v1 file format #26
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In preparation for adding a new packed-refs file format, extract all code from refs/packed-backend.c that involves knowledge of the plaintext file format. This includes any parsing logic that cares about the header, plaintext lines of the form "<oid> <ref>" or "^<peeled>", and the error messages when there is an issue in the file. This also includes the writing logic that writes the header or the individual references. Future changes will perform more refactoring to abstract away more of the writing process to be more generic, but this is enough of a chunk of code movement. Signed-off-by: Derrick Stolee <derrickstolee@github.com>
The write_with_updates() method uses a write_error label to jump to code that adds an error message before exiting with an error. This appears both when the packed-refs file header is written, but also when a ref line is written to the packed-refs file. A future change will abstract the loop that writes the refs out of write_with_updates(), making the goto an inconvenient pattern. For now, remove the distinction between "goto write_error" and "goto error" by adding the message in-line using the new static method add_write_error(). This is functionally equivalent, but will make the next step easier. Signed-off-by: Derrick Stolee <derrickstolee@github.com>
TBD Signed-off-by: Derrick Stolee <derrickstolee@github.com>
The packed-refs file is a plaintext file format that starts with a header line, then each ref is given as one or two lines (two if there is a peeled value). These lines are written as part of a sequence of updates which are merged with the existing ref iterator in merge_iterator_and_updates(). That method is currently tied directly to write_packed_entry_v1(). When creating a new version of the packed-file format, it would be valuable to use this merging logic in an identical way. Create a new function pointer type, write_ref_fn, and use that type in merge_iterator_and_updates(). Notably, the function pointer type no longer depends on a FILE pointer, but instead takes an arbitrary "void *write_data" parameter. This flexibility will be critical in the future, since the planned v2 format will use the chunk-format API and need a more complicated structure than the output FILE. Signed-off-by: Derrick Stolee <derrickstolee@github.com>
This was referenced Nov 4, 2022
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This is the fourth reviewable piece of the work to create the packed-refs v2 file format.
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