Merge branch 'ps/maintenance-detach-fix'

Maintenance tasks other than "gc" now properly go background when
"git maintenance" runs them.

* ps/maintenance-detach-fix:
  run-command: fix detaching when running auto maintenance
  builtin/maintenance: add a `--detach` flag
  builtin/gc: add a `--detach` flag
  builtin/gc: stop processing log file on signal
  builtin/gc: fix leaking config values
  builtin/gc: refactor to read config into structure
  config: fix constness of out parameter for `git_config_get_expiry()`

Author: gitster

Documentation/config/gc.txt

@@ -40,7 +40,8 @@ use, it'll affect how the auto pack limit works.
 
 gc.autoDetach::
 	Make `git gc --auto` return immediately and run in the background
-	if the system supports it. Default is true.
+	if the system supports it. Default is true. This config variable acts
+	as a fallback in case `maintenance.autoDetach` is not set.
 
 gc.bigPackThreshold::
 	If non-zero, all non-cruft packs larger than this limit are kept

Documentation/config/maintenance.txt

@@ -3,6 +3,17 @@ maintenance.auto::
 	`git maintenance run --auto` after doing their normal work. Defaults
 	to true.
 
+maintenance.autoDetach::
+	Many Git commands trigger automatic maintenance after they have
+	written data into the repository. This boolean config option
+	controls whether this automatic maintenance shall happen in the
+	foreground or whether the maintenance process shall detach and
+	continue to run in the background.
++
+If unset, the value of `gc.autoDetach` is used as a fallback. Defaults
+to true if both are unset, meaning that the maintenance process will
+detach.
+
 maintenance.strategy::
 	This string config option provides a way to specify one of a few
 	recommended schedules for background maintenance. This only affects

Documentation/git-gc.txt

@@ -9,7 +9,7 @@ git-gc - Cleanup unnecessary files and optimize the local repository
 SYNOPSIS
 --------
 [verse]
-'git gc' [--aggressive] [--auto] [--quiet] [--prune=<date> | --no-prune] [--force] [--keep-largest-pack]
+'git gc' [--aggressive] [--auto] [--[no-]detach] [--quiet] [--prune=<date> | --no-prune] [--force] [--keep-largest-pack]
 
 DESCRIPTION
 -----------
@@ -53,6 +53,9 @@ configuration options such as `gc.auto` and `gc.autoPackLimit`, all
 other housekeeping tasks (e.g. rerere, working trees, reflog...) will
 be performed as well.
 
+--[no-]detach::
+	Run in the background if the system supports it. This option overrides
+	the `gc.autoDetach` config.
 
 --[no-]cruft::
 	When expiring unreachable objects, pack them separately into a