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commit: add generation number to struct commit

The generation number of a commit is defined recursively as follows:

* If a commit A has no parents, then the generation number of A is one.
* If a commit A has parents, then the generation number of A is one
  more than the maximum generation number among the parents of A.

Add a uint32_t generation field to struct commit so we can pass this
information to revision walks. We use three special values to signal
the generation number is invalid:

GENERATION_NUMBER_INFINITY 0xFFFFFFFF
GENERATION_NUMBER_MAX 0x3FFFFFFF
GENERATION_NUMBER_ZERO 0

The first (_INFINITY) means the generation number has not been loaded or
computed. The second (_MAX) means the generation number is too large to
store in the commit-graph file. The third (_ZERO) means the generation
number was loaded from a commit graph file that was written by a version
of git that did not support generation numbers.

Signed-off-by: Derrick Stolee <dstolee@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
tags/v2.19.0-rc0
Derrick Stolee Junio C Hamano 1 year ago
parent
commit
83073cc994
3 changed files with 7 additions and 0 deletions
  1. +1
    -0
      alloc.c
  2. +2
    -0
      commit-graph.c
  3. +4
    -0
      commit.h

+ 1
- 0
alloc.c View File

@@ -94,6 +94,7 @@ void *alloc_commit_node(void)
c->object.type = OBJ_COMMIT;
c->index = alloc_commit_index();
c->graph_pos = COMMIT_NOT_FROM_GRAPH;
c->generation = GENERATION_NUMBER_INFINITY;
return c;
}



+ 2
- 0
commit-graph.c View File

@@ -262,6 +262,8 @@ static int fill_commit_in_graph(struct commit *item, struct commit_graph *g, uin
date_low = get_be32(commit_data + g->hash_len + 12);
item->date = (timestamp_t)((date_high << 32) | date_low);

item->generation = get_be32(commit_data + g->hash_len + 8) >> 2;

pptr = &item->parents;

edge_value = get_be32(commit_data + g->hash_len);


+ 4
- 0
commit.h View File

@@ -10,6 +10,9 @@
#include "pretty.h"

#define COMMIT_NOT_FROM_GRAPH 0xFFFFFFFF
#define GENERATION_NUMBER_INFINITY 0xFFFFFFFF
#define GENERATION_NUMBER_MAX 0x3FFFFFFF
#define GENERATION_NUMBER_ZERO 0

struct commit_list {
struct commit *item;
@@ -30,6 +33,7 @@ struct commit {
*/
struct tree *maybe_tree;
uint32_t graph_pos;
uint32_t generation;
};

extern int save_commit_buffer;


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