git-p4: Allow filtering Perforce branches by user

All branches in the Perforce server are downloaded to allow branch detection. If
you have a centralized server on a remote location and there is a big number of
branches this operation can take some time.
This patch adds the configuration option git-p4.branchUser to allow filtering
the branch list by user. Although this limits the branch maintenance in Perforce
to be done by a single user, it might be an advantage when the number of
branches being used in a specific depot is very small when compared with the
branches available in the server.

Signed-off-by: Vitor Antunes <vitor.hda@gmail.com>
Acked-by: Pete Wyckoff <pw@padd.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

contrib/fast-import/git-p4

@@ -1455,7 +1455,13 @@ class P4Sync(Command, P4UserMap):
     def getBranchMapping(self):
         lostAndFoundBranches = set()
 
-        for info in p4CmdList("branches"):
+        user = gitConfig("git-p4.branchUser")
+        if len(user) > 0:
+            command = "branches -u %s" % user
+        else:
+            command = "branches"
+
+        for info in p4CmdList(command):
             details = p4Cmd("branch -o %s" % info["branch"])
             viewIdx = 0
             while details.has_key("View%s" % viewIdx):

contrib/fast-import/git-p4.txt

@@ -257,6 +257,12 @@ Perforce server. Will enable --find-copies-harder git argument.
 
   git config [--global] git-p4.detectCopies true
 
+git-p4.branchUser
+
+Only use branch specifications defined by the selected username.
+
+  git config [--global] git-p4.branchUser username
+
 Implementation Details...
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