Merge branch 'ah/show-ref-usage-string'

Both "git show-ref -h" and "git show-ref --help" illustrated that the
"--exclude-existing" option makes the command read list of refs
from its standard input.  Change only the "show-ref -h" output to
have a pair of "<>" around the placeholder that designate an input
file, i.e. "git show-ref --exclude-existing < <ref-list>".

* ah/show-ref-usage-string:
  show-ref: place angle brackets around variables in usage string

builtin/show-ref.c

@@ -8,7 +8,7 @@
 
 static const char * const show_ref_usage[] = {
 	N_("git show-ref [-q | --quiet] [--verify] [--head] [-d | --dereference] [-s | --hash[=<n>]] [--abbrev[=<n>]] [--tags] [--heads] [--] [<pattern>...]"),
-	N_("git show-ref --exclude-existing[=pattern] < ref-list"),
+	N_("git show-ref --exclude-existing[=<pattern>] < <ref-list>"),
 	NULL
 };