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pseudo-merge: implement support for reading pseudo-merge commits

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Implement the basic API for reading pseudo-merge bitmaps, which consists
of four basic functions:

  - pseudo_merge_bitmap()
  - use_pseudo_merge()
  - apply_pseudo_merges_for_commit()
  - cascade_pseudo_merges()

These functions are all documented in pseudo-merge.h, but their rough
descriptions are as follows:

  - pseudo_merge_bitmap() reads and inflates the objects EWAH bitmap for
    a given pseudo-merge

  - use_pseudo_merge() does the same as pseudo_merge_bitmap(), but on
    the commits EWAH bitmap, not the objects bitmap

  - apply_pseudo_merges_for_commit() applies all satisfied pseudo-merge
    commits for a given result set, and cascades any yet-unsatisfied
    pseudo-merges if any were applied in the previous step

  - cascade_pseudo_merges() applies all pseudo-merges which are
    satisfied but have not been previously applied, repeating this
    process until no more pseudo-merges can be applied

The core of the API is the latter two functions, which are responsible
for applying pseudo-merges during the object traversal implemented in
the pack-bitmap machinery.

The other two functions (pseudo_merge_bitmap(), and use_pseudo_merge())
are low-level ways to interact with the pseudo-merge machinery, which
will be useful in future commits.

Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Taylor Blau
2024-05-23 17:26:58 -04:00
committed by Junio C Hamano
parent 7c0fae8844
commit 955747b4da
2 changed files with 279 additions and 0 deletions
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44
pseudo-merge.h
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@@ -162,4 +162,48 @@ struct pseudo_merge {
*/
void free_pseudo_merge_map(struct pseudo_merge_map *pm);
/*
* Loads the bitmap corresponding to the given pseudo-merge from the
* map, if it has not already been loaded.
*/
struct ewah_bitmap *pseudo_merge_bitmap(const struct pseudo_merge_map *pm,
struct pseudo_merge *merge);
/*
* Loads the pseudo-merge and its commits bitmap from the given
* pseudo-merge map, if it has not already been loaded.
*/
struct pseudo_merge *use_pseudo_merge(const struct pseudo_merge_map *pm,
struct pseudo_merge *merge);
/*
* Applies pseudo-merge(s) containing the given commit to the bitmap
* "result".
*
* If any pseudo-merge(s) were satisfied, returns the number
* satisfied, otherwise returns 0. If any were satisfied, the
* remaining unsatisfied pseudo-merges are cascaded (see below).
*/
int apply_pseudo_merges_for_commit(const struct pseudo_merge_map *pm,
struct bitmap *result,
struct commit *commit, uint32_t commit_pos);
/*
* Applies pseudo-merge(s) which are satisfied according to the
* current bitmap in result (or roots, see below). If any
* pseudo-merges were satisfied, repeat the process over unsatisfied
* pseudo-merge commits until no more pseudo-merges are satisfied.
*
* Result is the bitmap to which the pseudo-merge(s) are applied.
* Roots (if given) is a bitmap of the traversal tip(s) for either
* side of a reachability traversal.
*
* Roots may given instead of a populated results bitmap at the
* beginning of a traversal on either side where the reachability
* closure over tips is not yet known.
*/
int cascade_pseudo_merges(const struct pseudo_merge_map *pm,
struct bitmap *result,
struct bitmap *roots);
#endif