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Packed-refs v2 Part IV: abstract some parts of the v1 file format #26

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Packed-refs v2 Part IV: abstract some parts of the v1 file format #26

wants to merge 4 commits into from

Commits on Nov 3, 2022

  1. refs: extract packfile format to new file 

    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>
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    derrickstolee committed Nov 3, 2022
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  2. packed-backend: extract add_write_error() 

    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>
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    derrickstolee committed Nov 3, 2022
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  3. packed-backend: extract iterator/updates merge 

    TBD

Signed-off-by: Derrick Stolee <derrickstolee@github.com>
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    derrickstolee committed Nov 3, 2022
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  4. packed-backend: create abstraction for writing refs 

    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>
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    derrickstolee committed Nov 3, 2022
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