Merge branch 'ds/feature-macros' into pu

A mechanism to affect the default setting for a (related) group of
configuration variables is introduced.

* ds/feature-macros:
  repo-settings: create feature.experimental setting
  repo-settings: create feature.manyFiles setting
  repo-settings: parse core.untrackedCache
  commit-graph: turn on commit-graph by default
  t6501: use 'git gc' in quiet mode
  repo-settings: consolidate some config settings

Author: gitster

Documentation/config.txt

@@ -345,6 +345,8 @@ include::config/difftool.txt[]
 
 include::config/fastimport.txt[]
 
+include::config/feature.txt[]
+
 include::config/fetch.txt[]
 
 include::config/format.txt[]

Documentation/config/core.txt

@@ -86,7 +86,9 @@ core.untrackedCache::
 	it will automatically be removed, if set to `false`. Before
 	setting it to `true`, you should check that mtime is working
 	properly on your system.
-	See linkgit:git-update-index[1]. `keep` by default.
+	See linkgit:git-update-index[1]. `keep` by default, unless
+	`feature.manyFiles` is enabled which sets this setting to
+	`true` by default.
 
 core.checkStat::
 	When missing or is set to `default`, many fields in the stat
@@ -577,7 +579,7 @@ the `GIT_NOTES_REF` environment variable.  See linkgit:git-notes[1].
 
 core.commitGraph::
 	If true, then git will read the commit-graph file (if it exists)
-	to parse the graph structure of commits. Defaults to false. See
+	to parse the graph structure of commits. Defaults to true. See
 	linkgit:git-commit-graph[1] for more information.
 
 core.useReplaceRefs::

Documentation/config/feature.txt

@@ -0,0 +1,29 @@
+feature.*::
+	The config settings that start with `feature.` modify the defaults of
+	a group of other config settings. These groups are created by the Git
+	developer community as recommended defaults and are subject to change.
+	In particular, new config options may be added with different defaults.
+
+feature.experimental::
+	Enable config options that are new to Git, and are being considered for
+	future defaults. Config settings included here may be added or removed
+	with each release, including minor version updates. These settings may
+	have unintended interactions since they are so new. Please enable this
+	setting if you are interested in providing feedback on experimental
+	features. The new default values are:
++
+* `pack.useSparse=true` uses a new algorithm when constructing a pack-file
+which can improve `git push` performance in repos with many files.
++
+* `fetch.negotiationAlgorithm=skipping` may improve fetch negotiation times by
+skipping more commits at a time, reducing the number of round trips.
+
+feature.manyFiles::
+	Enable config options that optimize for repos with many files in the
+	working directory. With many files, commands such as `git status` and
+	`git checkout` may be slow and these new defaults improve performance:
++
+* `index.version=4` enables path-prefix compression in the index.
++
+* `core.untrackedCache=true` enables the untracked cache. This setting assumes
+that mtime is working on your machine.

Documentation/config/fetch.txt

@@ -59,7 +59,8 @@ fetch.negotiationAlgorithm::
 	effort to converge faster, but may result in a larger-than-necessary
 	packfile; The default is "default" which instructs Git to use the default algorithm
 	that never skips commits (unless the server has acknowledged it or one
-	of its descendants).
+	of its descendants). If `feature.experimental` is enabled, then this
+	setting defaults to "skipping".
 	Unknown values will cause 'git fetch' to error out.
 +
 See also the `--negotiation-tip` option for linkgit:git-fetch[1].

Documentation/config/gc.txt

@@ -63,7 +63,7 @@ gc.writeCommitGraph::
 	If true, then gc will rewrite the commit-graph file when
 	linkgit:git-gc[1] is run. When using `git gc --auto`
 	the commit-graph will be updated if housekeeping is
-	required. Default is false. See linkgit:git-commit-graph[1]
+	required. Default is true. See linkgit:git-commit-graph[1]
 	for details.
 
 gc.logExpiry::

Documentation/config/index.txt

@@ -24,3 +24,4 @@ index.threads::
 index.version::
 	Specify the version with which new index files should be
 	initialized.  This does not affect existing repositories.
+	If `feature.manyFiles` is enabled, then the default is 4.

Documentation/config/pack.txt

@@ -112,7 +112,8 @@ pack.useSparse::
 	objects. This can have significant performance benefits when
 	computing a pack to send a small change. However, it is possible
 	that extra objects are added to the pack-file if the included
-	commits contain certain types of direct renames.
+	commits contain certain types of direct renames. Default is `false`
+	unless `feature.experimental` is enabled.
 
 pack.writeBitmaps (deprecated)::
 	This is a deprecated synonym for `repack.writeBitmaps`.

Makefile

@@ -968,6 +968,7 @@ LIB_OBJS += refspec.o
 LIB_OBJS += ref-filter.o
 LIB_OBJS += remote.o
 LIB_OBJS += replace-object.o
+LIB_OBJS += repo-settings.o
 LIB_OBJS += repository.o
 LIB_OBJS += rerere.o
 LIB_OBJS += resolve-undo.o

builtin/gc.c

@@ -42,7 +42,6 @@ static int aggressive_depth = 50;
 static int aggressive_window = 250;
 static int gc_auto_threshold = 6700;
 static int gc_auto_pack_limit = 50;
-static int gc_write_commit_graph;
 static int detach_auto = 1;
 static timestamp_t gc_log_expire_time;
 static const char *gc_log_expire = "1.day.ago";
@@ -149,7 +148,6 @@ static void gc_config(void)
 	git_config_get_int("gc.aggressivedepth", &aggressive_depth);
 	git_config_get_int("gc.auto", &gc_auto_threshold);
 	git_config_get_int("gc.autopacklimit", &gc_auto_pack_limit);
-	git_config_get_bool("gc.writecommitgraph", &gc_write_commit_graph);
 	git_config_get_bool("gc.autodetach", &detach_auto);
 	git_config_get_expiry("gc.pruneexpire", &prune_expire);
 	git_config_get_expiry("gc.worktreepruneexpire", &prune_worktrees_expire);
@@ -686,11 +684,11 @@ int cmd_gc(int argc, const char **argv, const char *prefix)
 		clean_pack_garbage();
 	}
 
-	if (gc_write_commit_graph &&
-	    write_commit_graph_reachable(get_object_directory(),
-					 !quiet && !daemonized ? COMMIT_GRAPH_WRITE_PROGRESS : 0,
-					 NULL))
-		return 1;
+	prepare_repo_settings(the_repository);
+	if (the_repository->settings.gc_write_commit_graph == 1)
+		write_commit_graph_reachable(get_object_directory(),
+					     !quiet && !daemonized ? COMMIT_GRAPH_WRITE_PROGRESS : 0,
+					     NULL);
 
 	if (auto_gc && too_many_loose_objects())
 		warning(_("There are too many unreachable loose objects; "

builtin/pack-objects.c

@@ -2704,10 +2704,6 @@ static int git_pack_config(const char *k, const char *v, void *cb)
 		use_bitmap_index_default = git_config_bool(k, v);
 		return 0;
 	}
-	if (!strcmp(k, "pack.usesparse")) {
-		sparse = git_config_bool(k, v);
-		return 0;
-	}
 	if (!strcmp(k, "pack.threads")) {
 		delta_search_threads = git_config_int(k, v);
 		if (delta_search_threads < 0)
@@ -3332,6 +3328,10 @@ int cmd_pack_objects(int argc, const char **argv, const char *prefix)
 	read_replace_refs = 0;
 
 	sparse = git_env_bool("GIT_TEST_PACK_SPARSE", 0);
+	prepare_repo_settings(the_repository);
+	if (!sparse && the_repository->settings.pack_use_sparse != -1)
+		sparse = the_repository->settings.pack_use_sparse;
+
 	reset_pack_idx_option(&pack_idx_opts);
 	git_config(git_pack_config, NULL);