Merge branch 'jn/eject-fetch-write-commit-graph-out-of-experimental' into master

"fetch.writeCommitGraph" was enabled when "feature.experimental" is
asked for, but it was found to be a bit too risky even for bold
folks in its current shape.  The configuration has been ejected, at
least for now, from the "experimental" feature set.

* jn/eject-fetch-write-commit-graph-out-of-experimental:
  experimental: default to fetch.writeCommitGraph=false

Documentation/config/feature.txt

@@ -15,14 +15,6 @@ feature.experimental::
 * `fetch.negotiationAlgorithm=skipping` may improve fetch negotiation times by
 skipping more commits at a time, reducing the number of round trips.
 +
-* `fetch.writeCommitGraph=true` writes a commit-graph after every `git fetch`
-command that downloads a pack-file from a remote. Using the `--split` option,
-most executions will create a very small commit-graph file on top of the
-existing commit-graph file(s). Occasionally, these files will merge and the
-write may take longer. Having an updated commit-graph file helps performance
-of many Git commands, including `git merge-base`, `git push -f`, and
-`git log --graph`.
-+
 * `protocol.version=2` speeds up fetches from repositories with many refs by
 allowing the client to specify which refs to list before the server lists
 them.

Documentation/config/fetch.txt

@@ -90,5 +90,4 @@ fetch.writeCommitGraph::
 	the existing commit-graph file(s). Occasionally, these files will
 	merge and the write may take longer. Having an updated commit-graph
 	file helps performance of many Git commands, including `git merge-base`,
-	`git push -f`, and `git log --graph`. Defaults to false, unless
+	`git push -f`, and `git log --graph`. Defaults to false.
-	`feature.experimental` is true.

repo-settings.c

@@ -51,14 +51,14 @@ void prepare_repo_settings(struct repository *r)
 		UPDATE_DEFAULT_BOOL(r->settings.index_version, 4);
 		UPDATE_DEFAULT_BOOL(r->settings.core_untracked_cache, UNTRACKED_CACHE_WRITE);
 	}
+
 	if (!repo_config_get_bool(r, "fetch.writecommitgraph", &value))
 		r->settings.fetch_write_commit_graph = value;
-	if (!repo_config_get_bool(r, "feature.experimental", &value) && value) {
-		UPDATE_DEFAULT_BOOL(r->settings.fetch_negotiation_algorithm, FETCH_NEGOTIATION_SKIPPING);
-		UPDATE_DEFAULT_BOOL(r->settings.fetch_write_commit_graph, 1);
-	}
 	UPDATE_DEFAULT_BOOL(r->settings.fetch_write_commit_graph, 0);
 
+	if (!repo_config_get_bool(r, "feature.experimental", &value) && value)
+		UPDATE_DEFAULT_BOOL(r->settings.fetch_negotiation_algorithm, FETCH_NEGOTIATION_SKIPPING);
+
 	/* Hack for test programs like test-dump-untracked-cache */
 	if (ignore_untracked_cache_config)
 		r->settings.core_untracked_cache = UNTRACKED_CACHE_KEEP;