Merge branch 'ld/p4-detached-head' into maint

Make git-p4 work on a detached head.

* ld/p4-detached-head:
  git-p4: work with a detached head
  git-p4: add option to system() to return subshell status
  git-p4: add failing test for submit from detached head

git-p4.py

@@ -190,14 +190,16 @@ def p4_has_move_command():
     # assume it failed because @... was invalid changelist
     return True
 
-def system(cmd):
+def system(cmd, ignore_error=False):
     expand = isinstance(cmd,basestring)
     if verbose:
         sys.stderr.write("executing %s\n" % str(cmd))
     retcode = subprocess.call(cmd, shell=expand)
-    if retcode:
+    if retcode and not ignore_error:
         raise CalledProcessError(retcode, cmd)
 
+    return retcode
+
 def p4_system(cmd):
     """Specifically invoke p4 as the system command. """
     real_cmd = p4_build_cmd(cmd)
@@ -540,7 +542,12 @@ def p4Where(depotPath):
     return clientPath
 
 def currentGitBranch():
-    return read_pipe("git name-rev HEAD").split(" ")[1].strip()
+    retcode = system(["git", "symbolic-ref", "-q", "HEAD"], ignore_error=True)
+    if retcode != 0:
+        # on a detached head
+        return None
+    else:
+        return read_pipe(["git", "name-rev", "HEAD"]).split(" ")[1].strip()
 
 def isValidGitDir(path):
     if (os.path.exists(path + "/HEAD")
@@ -1649,8 +1656,6 @@ class P4Submit(Command, P4UserMap):
     def run(self, args):
         if len(args) == 0:
             self.master = currentGitBranch()
-            if len(self.master) == 0 or not gitBranchExists("refs/heads/%s" % self.master):
-                die("Detecting current git branch failed!")
         elif len(args) == 1:
             self.master = args[0]
             if not branchExists(self.master):
@@ -1658,9 +1663,10 @@ class P4Submit(Command, P4UserMap):
         else:
             return False
 
-        allowSubmit = gitConfig("git-p4.allowSubmit")
-        if len(allowSubmit) > 0 and not self.master in allowSubmit.split(","):
-            die("%s is not in git-p4.allowSubmit" % self.master)
+        if self.master:
+            allowSubmit = gitConfig("git-p4.allowSubmit")
+            if len(allowSubmit) > 0 and not self.master in allowSubmit.split(","):
+                die("%s is not in git-p4.allowSubmit" % self.master)
 
         [upstream, settings] = findUpstreamBranchPoint()
         self.depotPath = settings['depot-paths'][0]
@@ -1728,7 +1734,12 @@ class P4Submit(Command, P4UserMap):
         self.check()
 
         commits = []
-        for line in read_pipe_lines(["git", "rev-list", "--no-merges", "%s..%s" % (self.origin, self.master)]):
+        if self.master:
+            commitish = self.master
+        else:
+            commitish = 'HEAD'
+
+        for line in read_pipe_lines(["git", "rev-list", "--no-merges", "%s..%s" % (self.origin, commitish)]):
             commits.append(line.strip())
         commits.reverse()
 

t/t9800-git-p4-basic.sh

@@ -241,6 +241,22 @@ test_expect_success 'unresolvable host in P4PORT should display error' '
 	)
 '
 
+test_expect_success 'submit from detached head' '
+	test_when_finished cleanup_git &&
+	git p4 clone --dest="$git" //depot &&
+	(
+		cd "$git" &&
+		git checkout p4/master &&
+		>detached_head_test &&
+		git add detached_head_test &&
+		git commit -m "add detached_head" &&
+		git config git-p4.skipSubmitEdit true &&
+		git p4 submit &&
+		git p4 rebase &&
+		git log p4/master | grep detached_head
+	)
+'
+
 test_expect_success 'kill p4d' '
 	kill_p4d
 '