Merge branch 'ls/p4-keep-empty-commits'

"git p4" used to import Perforce CLs that touch only paths outside
the client spec as empty commits.  It has been corrected to ignore
them instead, with a new configuration git-p4.keepEmptyCommits as a
backward compatibility knob.

* ls/p4-keep-empty-commits:
  git-p4: add option to keep empty commits

Documentation/git-p4.txt

@@ -549,6 +549,10 @@ git-p4.largeFilePush::
 	Boolean variable which defines if large files are automatically
 	pushed to a server.
 
+git-p4.keepEmptyCommits::
+	A changelist that contains only excluded files will be imported
+	as an empty commit if this boolean option is set to true.
+
 Submit variables
 ~~~~~~~~~~~~~~~~
 git-p4.detectRenames::