Merge branch 'ds/decorate-filter-tweak'

The namespaces used by "log --decorate" from "refs/" hierarchy by
default has been tightened.

* ds/decorate-filter-tweak:
  fetch: use ref_namespaces during prefetch
  maintenance: stop writing log.excludeDecoration
  log: create log.initialDecorationSet=all
  log: add --clear-decorations option
  log: add default decoration filter
  log-tree: use ref_namespaces instead of if/else-if
  refs: use ref_namespaces for replace refs base
  refs: add array of ref namespaces
  t4207: test coloring of grafted decorations
  t4207: modernize test
  refs: allow "HEAD" as decoration filter

Documentation/config/log.txt

@@ -18,6 +18,11 @@ log.decorate::
 	names are shown. This is the same as the `--decorate` option
 	of the `git log`.
 
+log.initialDecorationSet::
+	By default, `git log` only shows decorations for certain known ref
+	namespaces. If 'all' is specified, then show all refs as
+	decorations.
+
 log.excludeDecoration::
 	Exclude the specified patterns from the log decorations. This is
 	similar to the `--decorate-refs-exclude` command-line option, but

Documentation/git-log.txt

@@ -45,13 +45,23 @@ OPTIONS
 
 --decorate-refs=<pattern>::
 --decorate-refs-exclude=<pattern>::
-	If no `--decorate-refs` is given, pretend as if all refs were
-	included.  For each candidate, do not use it for decoration if it
+	For each candidate reference, do not use it for decoration if it
 	matches any patterns given to `--decorate-refs-exclude` or if it
 	doesn't match any of the patterns given to `--decorate-refs`. The
 	`log.excludeDecoration` config option allows excluding refs from
 	the decorations, but an explicit `--decorate-refs` pattern will
 	override a match in `log.excludeDecoration`.
++
+If none of these options or config settings are given, then references are
+used as decoration if they match `HEAD`, `refs/heads/`, `refs/remotes/`,
+`refs/stash/`, or `refs/tags/`.
+
+--clear-decorations::
+	When specified, this option clears all previous `--decorate-refs`
+	or `--decorate-refs-exclude` options and relaxes the default
+	decoration filter to include all references. This option is
+	assumed if the config value `log.initialDecorationSet` is set to
+	`all`.
 
 --source::
 	Print out the ref name given on the command line by which each