[PATCH 11/12] fetch: compute commit-graph by default

[Derrick Stolee]

During a call to 'git fetch', we expect new commits and updated refs.
Use these updated refs to add the new commits to the commit-graph file,
automatically providing performance benefits in other calls.

Use 'fetch.commitGraph' config setting to enable or disable this
behavior. Defaults to false while the commit-graph feature matures.
Specifically, we do not want this on by default until the commit-graph
feature integrates with history-modifying features such as shallow
clones.

Signed-off-by: Derrick Stolee <dsto...@microsoft.com>
---
 Documentation/config.txt |  4 ++++
 builtin/fetch.c          | 13 +++++++++++++
 2 files changed, 17 insertions(+)

diff --git a/Documentation/config.txt b/Documentation/config.txt
index 9a3abd87e7..3d8225600a 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -1409,6 +1409,10 @@ fetch.output::
        `full` and `compact`. Default value is `full`. See section
        OUTPUT in linkgit:git-fetch[1] for detail.
 
+fetch.commitGraph::
+       If true, fetch will automatically update the commit-graph file.
+       See linkgit:git-commit-graph[1].
+
 format.attach::
        Enable multipart/mixed attachments as the default for
        'format-patch'.  The value can also be a double quoted string
diff --git a/builtin/fetch.c b/builtin/fetch.c
index 8ee998ea2e..254f6ecfb6 100644
--- a/builtin/fetch.c
+++ b/builtin/fetch.c
@@ -38,6 +38,7 @@ enum {
 static int fetch_prune_config = -1; /* unspecified */
 static int prune = -1; /* unspecified */
 #define PRUNE_BY_DEFAULT 0 /* do we prune by default? */
+static int fetch_commit_graph = 0;
 
 static int all, append, dry_run, force, keep, multiple, update_head_ok, 
verbosity, deepen_relative;
 static int progress = -1;
@@ -66,6 +67,11 @@ static int git_fetch_config(const char *k, const char *v, 
void *cb)
                return 0;
        }
 
+       if (!strcmp(k, "fetch.commitGraph")) {
+               fetch_commit_graph = git_config_bool(k, v);
+               return 0;
+       }
+
        if (!strcmp(k, "submodule.recurse")) {
                int r = git_config_bool(k, v) ?
                        RECURSE_SUBMODULES_ON : RECURSE_SUBMODULES_OFF;
@@ -1462,6 +1468,13 @@ int cmd_fetch(int argc, const char **argv, const char 
*prefix)
                result = fetch_multiple(&list);
        }
 
+       if (!result && fetch_commit_graph) {
+               struct argv_array commit_graph = ARGV_ARRAY_INIT;
+               argv_array_pushl(&commit_graph, "commit-graph", "write", 
"--reachable", NULL);
+               if (run_command_v_opt(commit_graph.argv, RUN_GIT_CMD))
+                       result = 1;
+       }
+
        if (!result && (recurse_submodules != RECURSE_SUBMODULES_OFF)) {
                struct argv_array options = ARGV_ARRAY_INIT;
 
-- 
2.16.2.329.gfb62395de6