mirrors/git
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

builtin/commit-graph.c: introduce split strategy 'replace'

Browse Source 
When using split commit-graphs, it is sometimes useful to completely
replace the commit-graph chain with a new base.

For example, consider a scenario in which a repository builds a new
commit-graph incremental for each push. Occasionally (say, after some
fixed number of pushes), they may wish to rebuild the commit-graph chain
with all reachable commits.

They can do so with

  $ git commit-graph write --reachable

but this removes the chain entirely and replaces it with a single
commit-graph in 'objects/info/commit-graph'. Unfortunately, this means
that the next push will have to move this commit-graph into the first
layer of a new chain, and then write its new commits on top.

Avoid such copying entirely by allowing the caller to specify that they
wish to replace the entirety of their commit-graph chain, while also
specifying that the new commit-graph should become the basis of a fresh,
length-one chain.

This addresses the above situation by making it possible for the caller
to instead write:

  $ git commit-graph write --reachable --split=replace

which writes a new length-one chain to 'objects/info/commit-graphs',
making the commit-graph incremental generated by the subsequent push
relatively cheap by avoiding the aforementioned copy.

In order to do this, remove an assumption in 'write_commit_graph_file'
that chains are always at least two incrementals long.

Signed-off-by: Taylor Blau <me@ttaylorr.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Taylor Blau
2020-04-13 22:04:17 -06:00
committed by Junio C Hamano
parent fdbde82fe5
commit 8a6ac287b2
5 changed files with 66 additions and 18 deletions
Download Patch File Download Diff File Expand all files Collapse all files

53
commit-graph.c
View File

@ -866,7 +866,7 @@ static void write_graph_chunk_data(struct hashfile *f, int hash_len,
if (edge_value >= 0)
edge_value += ctx->new_num_commits_in_base;
else {
else if (ctx->new_base_graph) {
uint32_t pos;
if (find_commit_in_graph(parent->item,
ctx->new_base_graph,
@ -897,7 +897,7 @@ static void write_graph_chunk_data(struct hashfile *f, int hash_len,
if (edge_value >= 0)
edge_value += ctx->new_num_commits_in_base;
else {
else if (ctx->new_base_graph) {
uint32_t pos;
if (find_commit_in_graph(parent->item,
ctx->new_base_graph,
@ -964,7 +964,7 @@ static void write_graph_chunk_extra_edges(struct hashfile *f,
if (edge_value >= 0)
edge_value += ctx->new_num_commits_in_base;
else {
else if (ctx->new_base_graph) {
uint32_t pos;
if (find_commit_in_graph(parent->item,
ctx->new_base_graph,
@ -1037,6 +1037,8 @@ static void close_reachable(struct write_commit_graph_context *ctx)
{
int i;
struct commit *commit;
enum commit_graph_split_flags flags = ctx->split_opts ?
ctx->split_opts->flags : COMMIT_GRAPH_SPLIT_UNSPECIFIED;
if (ctx->report_progress)
ctx->progress = start_delayed_progress(
@ -1066,8 +1068,9 @@ static void close_reachable(struct write_commit_graph_context *ctx)
if (!commit)
continue;
if (ctx->split) {
if (!parse_commit(commit) &&
commit->graph_pos == COMMIT_NOT_FROM_GRAPH)
if ((!parse_commit(commit) &&
commit->graph_pos == COMMIT_NOT_FROM_GRAPH) ||
flags == COMMIT_GRAPH_SPLIT_REPLACE)
add_missing_parents(ctx, commit);
} else if (!parse_commit_no_graph(commit))
add_missing_parents(ctx, commit);
@ -1287,6 +1290,8 @@ static uint32_t count_distinct_commits(struct write_commit_graph_context *ctx)
static void copy_oids_to_commits(struct write_commit_graph_context *ctx)
{
uint32_t i;
enum commit_graph_split_flags flags = ctx->split_opts ?
ctx->split_opts->flags : COMMIT_GRAPH_SPLIT_UNSPECIFIED;
ctx->num_extra_edges = 0;
if (ctx->report_progress)
@ -1303,11 +1308,14 @@ static void copy_oids_to_commits(struct write_commit_graph_context *ctx)
ALLOC_GROW(ctx->commits.list, ctx->commits.nr + 1, ctx->commits.alloc);
ctx->commits.list[ctx->commits.nr] = lookup_commit(ctx->r, &ctx->oids.list[i]);
if (ctx->split &&
if (ctx->split && flags != COMMIT_GRAPH_SPLIT_REPLACE &&
ctx->commits.list[ctx->commits.nr]->graph_pos != COMMIT_NOT_FROM_GRAPH)
continue;
parse_commit_no_graph(ctx->commits.list[ctx->commits.nr]);
if (ctx->split && flags == COMMIT_GRAPH_SPLIT_REPLACE)
parse_commit(ctx->commits.list[ctx->commits.nr]);
else
parse_commit_no_graph(ctx->commits.list[ctx->commits.nr]);
num_parents = commit_list_count(ctx->commits.list[ctx->commits.nr]->parents);
if (num_parents > 2)
@ -1488,8 +1496,12 @@ static int write_commit_graph_file(struct write_commit_graph_context *ctx)
}
if (ctx->base_graph_name) {
const char *dest = ctx->commit_graph_filenames_after[
ctx->num_commit_graphs_after - 2];
const char *dest;
int idx = ctx->num_commit_graphs_after - 1;
if (ctx->num_commit_graphs_after > 1)
idx--;
dest = ctx->commit_graph_filenames_after[idx];
if (strcmp(ctx->base_graph_name, dest)) {
result = rename(ctx->base_graph_name, dest);
@ -1546,9 +1558,13 @@ static void split_graph_merge_strategy(struct write_commit_graph_context *ctx)
g = ctx->r->objects->commit_graph;
num_commits = ctx->commits.nr;
ctx->num_commit_graphs_after = ctx->num_commit_graphs_before + 1;
if (flags == COMMIT_GRAPH_SPLIT_REPLACE)
ctx->num_commit_graphs_after = 1;
else
ctx->num_commit_graphs_after = ctx->num_commit_graphs_before + 1;
if (flags != COMMIT_GRAPH_SPLIT_MERGE_PROHIBITED) {
if (flags != COMMIT_GRAPH_SPLIT_MERGE_PROHIBITED &&
flags != COMMIT_GRAPH_SPLIT_REPLACE) {
while (g && (g->num_commits <= size_mult * num_commits ||
(max_commits && num_commits > max_commits))) {
if (g->odb != ctx->odb)
@ -1561,7 +1577,11 @@ static void split_graph_merge_strategy(struct write_commit_graph_context *ctx)
}
}
ctx->new_base_graph = g;
if (flags != COMMIT_GRAPH_SPLIT_REPLACE)
ctx->new_base_graph = g;
else if (ctx->num_commit_graphs_after != 1)
BUG("split_graph_merge_strategy: num_commit_graphs_after "
"should be 1 with --split=replace");
if (ctx->num_commit_graphs_after == 2) {
char *old_graph_name = get_commit_graph_filename(g->odb);
@ -1772,6 +1792,7 @@ int write_commit_graph(struct object_directory *odb,
struct write_commit_graph_context *ctx;
uint32_t i, count_distinct = 0;
int res = 0;
int replace = 0;
if (!commit_graph_compatible(the_repository))
return 0;
@ -1806,6 +1827,9 @@ int write_commit_graph(struct object_directory *odb,
g = g->base_graph;
}
}
if (ctx->split_opts)
replace = ctx->split_opts->flags & COMMIT_GRAPH_SPLIT_REPLACE;
}
ctx->approx_nr_objects = approximate_object_count();
@ -1866,13 +1890,14 @@ int write_commit_graph(struct object_directory *odb,
goto cleanup;
}
if (!ctx->commits.nr)
if (!ctx->commits.nr && !replace)
goto cleanup;
if (ctx->split) {
split_graph_merge_strategy(ctx);
merge_commit_graphs(ctx);
if (!replace)
merge_commit_graphs(ctx);
} else
ctx->num_commit_graphs_after = 1;