Merge branch 'pw/p4-branch-fixes'

Fix "git p4" around branch handling.

* pw/p4-branch-fixes:
  git p4: fix submit when no master branch
  git p4 test: keep P4CLIENT changes inside subshells
  git p4: fix sync --branch when no master branch
  git p4: fail gracefully on sync with no master branch
  git p4: rearrange self.initialParent use
  git p4: allow short ref names to --branch
  git p4 doc: fix branch detection example
  git p4: clone --branch should checkout master
  git p4: verify expected refs in clone --bare test
  git p4: create p4/HEAD on initial clone
  git p4: inline listExistingP4GitBranches
  git p4: add comments to p4BranchesInGit
  git p4: rearrange and simplify hasOrigin handling
  git p4: test sync/clone --branch behavior

4 files changed, 253 insertions, 58 deletions

diff --git a/Documentation/git-p4.txt b/Documentation/git-p4.txt
index beff6229c8..f70ef9ded2 100644
--- a/Documentation/git-p4.txt
+++ b/Documentation/git-p4.txt
@@ -112,6 +112,11 @@ will be fetched and consulted first during a 'git p4 sync'.  Since
 importing directly from p4 is considerably slower than pulling changes
 from a git remote, this can be useful in a multi-developer environment.
 
+If there are multiple branches, doing 'git p4 sync' will automatically
+use the "BRANCH DETECTION" algorithm to try to partition new changes
+into the right branch.  This can be overridden with the '--branch'
+option to specify just a single branch to update.
+
 
 Rebase
 ~~~~~~
@@ -173,9 +178,11 @@ subsequent 'sync' operations.
 
 --branch <branch>::
 	Import changes into given branch.  If the branch starts with
-	'refs/', it will be used as is, otherwise the path 'refs/heads/'
-	will be prepended.  The default branch is 'master'.  If used
-	with an initial clone, no HEAD will be checked out.
+	'refs/', it will be used as is.  Otherwise if it does not start
+	with 'p4/', that prefix is added.  The branch is assumed to
+	name a remote tracking, but this can be modified using
+	'--import-local', or by giving a full ref name.  The default
+	branch is 'master'.
 +
 This example imports a new remote "p4/proj2" into an existing
 git repository:
@@ -287,6 +294,11 @@ These options can be used to modify 'git p4 submit' behavior.
 	to bypass the prompt, causing conflicting commits to be automatically
 	skipped, or to quit trying to apply commits, without prompting.
 
+--branch <branch>::
+	After submitting, sync this named branch instead of the default
+	p4/master.  See the "Sync options" section above for more
+	information.
+
 Rebase options
 ~~~~~~~~~~~~~~
 These options can be used to modify 'git p4 rebase' behavior.
@@ -394,8 +406,10 @@ the path elements in the p4 repository.  The example above relied on the
 presence of the p4 branch.  Without p4 branches, the same result will
 occur with:
 ----
+git init depot
+cd depot
 git config git-p4.branchList main:branch1
-git p4 clone --detect-branches //depot@all
+git p4 clone --detect-branches //depot@all .
 ----
 
 
diff --git a/git-p4.py b/git-p4.py
index 69f1452cf8..2da564995d 100755
--- a/git-p4.py
+++ b/git-p4.py
@@ -553,29 +553,49 @@ def gitConfigList(key):
         _gitConfig[key] = read_pipe("git config --get-all %s" % key, ignore_error=True).strip().split(os.linesep)
     return _gitConfig[key]
 
-def p4BranchesInGit(branchesAreInRemotes = True):
+def p4BranchesInGit(branchesAreInRemotes=True):
+    """Find all the branches whose names start with "p4/", looking
+       in remotes or heads as specified by the argument.  Return
+       a dictionary of { branch: revision } for each one found.
+       The branch names are the short names, without any
+       "p4/" prefix."""
+
     branches = {}
 
     cmdline = "git rev-parse --symbolic "
     if branchesAreInRemotes:
-        cmdline += " --remotes"
+        cmdline += "--remotes"
     else:
-        cmdline += " --branches"
+        cmdline += "--branches"
 
     for line in read_pipe_lines(cmdline):
         line = line.strip()
 
-        ## only import to p4/
-        if not line.startswith('p4/') or line == "p4/HEAD":
+        # only import to p4/
+        if not line.startswith('p4/'):
+            continue
+        # special symbolic ref to p4/master
+        if line == "p4/HEAD":
             continue
-        branch = line
 
-        # strip off p4
-        branch = re.sub ("^p4/", "", line)
+        # strip off p4/ prefix
+        branch = line[len("p4/"):]
 
         branches[branch] = parseRevision(line)
+
     return branches
 
+def branch_exists(branch):
+    """Make sure that the given ref name really exists."""
+
+    cmd = [ "git", "rev-parse", "--symbolic", "--verify", branch ]
+    p = subprocess.Popen(cmd, stdout=subprocess.PIPE, stderr=subprocess.PIPE)
+    out, _ = p.communicate()
+    if p.returncode:
+        return False
+    # expect exactly one line of output: the branch name
+    return out.rstrip() == branch
+
 def findUpstreamBranchPoint(head = "HEAD"):
     branches = p4BranchesInGit()
     # map from depot-path to branch name
@@ -907,7 +927,8 @@ class P4Submit(Command, P4UserMap):
                 optparse.make_option("--dry-run", "-n", dest="dry_run", action="store_true"),
                 optparse.make_option("--prepare-p4-only", dest="prepare_p4_only", action="store_true"),
                 optparse.make_option("--conflict", dest="conflict_behavior",
-                                     choices=self.conflict_behavior_choices)
+                                     choices=self.conflict_behavior_choices),
+                optparse.make_option("--branch", dest="branch"),
         ]
         self.description = "Submit changes from git to the perforce depot."
         self.usage += " [name of git branch to submit into perforce depot]"
@@ -920,6 +941,7 @@ class P4Submit(Command, P4UserMap):
         self.isWindows = (platform.system() == "Windows")
         self.exportLabels = False
         self.p4HasMoveCommand = p4_has_move_command()
+        self.branch = None
 
     def check(self):
         if len(p4CmdList("opened ...")) > 0:
@@ -1656,6 +1678,8 @@ class P4Submit(Command, P4UserMap):
             print "All commits applied!"
 
             sync = P4Sync()
+            if self.branch:
+                sync.branch = self.branch
             sync.run([])
 
             rebase = P4Rebase()
@@ -2509,13 +2533,6 @@ class P4Sync(Command, P4UserMap):
                 branch = branch[len(self.projectName):]
             self.knownBranches[branch] = branch
 
-    def listExistingP4GitBranches(self):
-        # branches holds mapping from name to commit
-        branches = p4BranchesInGit(self.importIntoRemotes)
-        self.p4BranchesInGit = branches.keys()
-        for branch in branches.keys():
-            self.initialParents[self.refPrefix + branch] = branches[branch]
-
     def updateOptionDict(self, d):
         option_keys = {}
         if self.keepRepoPath:
@@ -2687,6 +2704,7 @@ class P4Sync(Command, P4UserMap):
                     files = self.extractFilesFromCommit(description)
                     self.commit(description, files, self.branch,
                                 self.initialParent)
+                    # only needed once, to connect to the previous commit
                     self.initialParent = ""
             except IOError:
                 print self.gitError.read()
@@ -2752,34 +2770,31 @@ class P4Sync(Command, P4UserMap):
     def run(self, args):
         self.depotPaths = []
         self.changeRange = ""
-        self.initialParent = ""
         self.previousDepotPaths = []
+        self.hasOrigin = False
 
         # map from branch depot path to parent branch
         self.knownBranches = {}
         self.initialParents = {}
-        self.hasOrigin = originP4BranchesExist()
-        if not self.syncWithOrigin:
-            self.hasOrigin = False
 
         if self.importIntoRemotes:
             self.refPrefix = "refs/remotes/p4/"
         else:
             self.refPrefix = "refs/heads/p4/"
 
-        if self.syncWithOrigin and self.hasOrigin:
-            if not self.silent:
-                print "Syncing with origin first by calling git fetch origin"
-            system("git fetch origin")
+        if self.syncWithOrigin:
+            self.hasOrigin = originP4BranchesExist()
+            if self.hasOrigin:
+                if not self.silent:
+                    print 'Syncing with origin first, using "git fetch origin"'
+                system("git fetch origin")
 
+        branch_arg_given = bool(self.branch)
         if len(self.branch) == 0:
             self.branch = self.refPrefix + "master"
             if gitBranchExists("refs/heads/p4") and self.importIntoRemotes:
                 system("git update-ref %s refs/heads/p4" % self.branch)
-                system("git branch -D p4");
-            # create it /after/ importing, when master exists
-            if not gitBranchExists(self.refPrefix + "HEAD") and self.importIntoRemotes and gitBranchExists(self.branch):
-                system("git symbolic-ref %sHEAD %s" % (self.refPrefix, self.branch))
+                system("git branch -D p4")
 
         # accept either the command-line option, or the configuration variable
         if self.useClientSpec:
@@ -2796,12 +2811,25 @@ class P4Sync(Command, P4UserMap):
         if args == []:
             if self.hasOrigin:
                 createOrUpdateBranchesFromOrigin(self.refPrefix, self.silent)
-            self.listExistingP4GitBranches()
+
+            # branches holds mapping from branch name to sha1
+            branches = p4BranchesInGit(self.importIntoRemotes)
+
+            # restrict to just this one, disabling detect-branches
+            if branch_arg_given:
+                short = self.branch.split("/")[-1]
+                if short in branches:
+                    self.p4BranchesInGit = [ short ]
+            else:
+                self.p4BranchesInGit = branches.keys()
 
             if len(self.p4BranchesInGit) > 1:
                 if not self.silent:
                     print "Importing from/into multiple branches"
                 self.detectBranches = True
+                for branch in branches.keys():
+                    self.initialParents[self.refPrefix + branch] = \
+                        branches[branch]
 
             if self.verbose:
                 print "branches: %s" % self.p4BranchesInGit
@@ -2838,13 +2866,21 @@ class P4Sync(Command, P4UserMap):
             if p4Change > 0:
                 self.depotPaths = sorted(self.previousDepotPaths)
                 self.changeRange = "@%s,#head" % p4Change
-                if not self.detectBranches:
-                    self.initialParent = parseRevision(self.branch)
                 if not self.silent and not self.detectBranches:
                     print "Performing incremental import into %s git branch" % self.branch
 
+        # accept multiple ref name abbreviations:
+        #    refs/foo/bar/branch -> use it exactly
+        #    p4/branch -> prepend refs/remotes/ or refs/heads/
+        #    branch -> prepend refs/remotes/p4/ or refs/heads/p4/
         if not self.branch.startswith("refs/"):
-            self.branch = "refs/heads/" + self.branch
+            if self.importIntoRemotes:
+                prepend = "refs/remotes/"
+            else:
+                prepend = "refs/heads/"
+            if not self.branch.startswith("p4/"):
+                prepend += "p4/"
+            self.branch = prepend + self.branch
 
         if len(args) == 0 and self.depotPaths:
             if not self.silent:
@@ -2955,8 +2991,21 @@ class P4Sync(Command, P4UserMap):
             else:
                 # catch "git p4 sync" with no new branches, in a repo that
                 # does not have any existing p4 branches
-                if len(args) == 0 and not self.p4BranchesInGit:
-                    die("No remote p4 branches.  Perhaps you never did \"git p4 clone\" in here.");
+                if len(args) == 0:
+                    if not self.p4BranchesInGit:
+                        die("No remote p4 branches.  Perhaps you never did \"git p4 clone\" in here.")
+
+                    # The default branch is master, unless --branch is used to
+                    # specify something else.  Make sure it exists, or complain
+                    # nicely about how to use --branch.
+                    if not self.detectBranches:
+                        if not branch_exists(self.branch):
+                            if branch_arg_given:
+                                die("Error: branch %s does not exist." % self.branch)
+                            else:
+                                die("Error: no branch %s; perhaps specify one with --branch." %
+                                    self.branch)
+
                 if self.verbose:
                     print "Getting p4 changes for %s...%s" % (', '.join(self.depotPaths),
                                                               self.changeRange)
@@ -2974,6 +3023,14 @@ class P4Sync(Command, P4UserMap):
 
                 self.updatedBranches = set()
 
+                if not self.detectBranches:
+                    if args:
+                        # start a new branch
+                        self.initialParent = ""
+                    else:
+                        # build on a previous revision
+                        self.initialParent = parseRevision(self.branch)
+
                 self.importChanges(changes)
 
                 if not self.silent:
@@ -3006,6 +3063,13 @@ class P4Sync(Command, P4UserMap):
                 read_pipe("git update-ref -d %s" % branch)
             os.rmdir(os.path.join(os.environ.get("GIT_DIR", ".git"), self.tempBranchLocation))
 
+        # Create a symbolic ref p4/HEAD pointing to p4/<branch> to allow
+        # a convenient shortcut refname "p4".
+        if self.importIntoRemotes:
+            head_ref = self.refPrefix + "HEAD"
+            if not gitBranchExists(head_ref) and gitBranchExists(self.branch):
+                system(["git", "symbolic-ref", head_ref, self.branch])
+
         return True
 
 class P4Rebase(Command):
@@ -3113,17 +3177,15 @@ class P4Clone(P4Sync):
 
         if not P4Sync.run(self, depotPaths):
             return False
-        if self.branch != "master":
-            if self.importIntoRemotes:
-                masterbranch = "refs/remotes/p4/master"
-            else:
-                masterbranch = "refs/heads/p4/master"
-            if gitBranchExists(masterbranch):
-                system("git branch master %s" % masterbranch)
-                if not self.cloneBare:
-                    system("git checkout -f")
-            else:
-                print "Could not detect main branch. No checkout/master branch created."
+
+        # create a master branch and check out a work tree
+        if gitBranchExists(self.branch):
+            system([ "git", "branch", "master", self.branch ])
+            if not self.cloneBare:
+                system([ "git", "checkout", "-f" ])
+        else:
+            print 'Not checking out any branch, use ' \
+                  '"git checkout -q -b master <branch>"'
 
         # auto-set this variable if invoked with --use-client-spec
         if self.useClientSpec_from_options:
diff --git a/t/t9800-git-p4-basic.sh b/t/t9800-git-p4-basic.sh
index 8c5979647f..166e75209f 100755
--- a/t/t9800-git-p4-basic.sh
+++ b/t/t9800-git-p4-basic.sh
@@ -160,9 +160,12 @@ test_expect_success 'clone --bare should make a bare repository' '
 	test_when_finished cleanup_git &&
 	(
 		cd "$git" &&
-		test ! -d .git &&
-		bare=`git config --get core.bare` &&
-		test "$bare" = true
+		test_path_is_missing .git &&
+		git config --get --bool core.bare true &&
+		git rev-parse --verify refs/remotes/p4/master &&
+		git rev-parse --verify refs/remotes/p4/HEAD &&
+		git rev-parse --verify refs/heads/master &&
+		git rev-parse --verify HEAD
 	)
 '
 
diff --git a/t/t9806-git-p4-options.sh b/t/t9806-git-p4-options.sh
index fa40cc8bb5..4f077eeca8 100755
--- a/t/t9806-git-p4-options.sh
+++ b/t/t9806-git-p4-options.sh
@@ -27,14 +27,102 @@ test_expect_success 'clone no --git-dir' '
 	test_must_fail git p4 clone --git-dir=xx //depot
 '
 
-test_expect_success 'clone --branch' '
+test_expect_success 'clone --branch should checkout master' '
 	git p4 clone --branch=refs/remotes/p4/sb --dest="$git" //depot &&
 	test_when_finished cleanup_git &&
 	(
 		cd "$git" &&
-		git ls-files >files &&
-		test_line_count = 0 files &&
-		test_path_is_file .git/refs/remotes/p4/sb
+		git rev-parse refs/remotes/p4/sb >sb &&
+		git rev-parse refs/heads/master >master &&
+		test_cmp sb master &&
+		git rev-parse HEAD >head &&
+		test_cmp sb head
+	)
+'
+
+test_expect_success 'sync when no master branch prints a nice error' '
+	test_when_finished cleanup_git &&
+	git p4 clone --branch=refs/remotes/p4/sb --dest="$git" //depot@2 &&
+	(
+		cd "$git" &&
+		test_must_fail git p4 sync 2>err &&
+		grep "Error: no branch refs/remotes/p4/master" err
+	)
+'
+
+test_expect_success 'sync --branch builds the full ref name correctly' '
+	test_when_finished cleanup_git &&
+	(
+		cd "$git" &&
+		git init &&
+
+		git p4 sync --branch=b1 //depot &&
+		git rev-parse --verify refs/remotes/p4/b1 &&
+		git p4 sync --branch=p4/b2 //depot &&
+		git rev-parse --verify refs/remotes/p4/b2 &&
+
+		git p4 sync --import-local --branch=h1 //depot &&
+		git rev-parse --verify refs/heads/p4/h1 &&
+		git p4 sync --import-local --branch=p4/h2 //depot &&
+		git rev-parse --verify refs/heads/p4/h2 &&
+
+		git p4 sync --branch=refs/stuff //depot &&
+		git rev-parse --verify refs/stuff
+	)
+'
+
+# engages --detect-branches code, which will do filename filtering so
+# no sync to either b1 or b2
+test_expect_success 'sync when two branches but no master should noop' '
+	test_when_finished cleanup_git &&
+	(
+		cd "$git" &&
+		git init &&
+		git p4 sync --branch=refs/remotes/p4/b1 //depot@2 &&
+		git p4 sync --branch=refs/remotes/p4/b2 //depot@2 &&
+		git p4 sync &&
+		git show -s --format=%s refs/remotes/p4/b1 >show &&
+		grep "Initial import" show &&
+		git show -s --format=%s refs/remotes/p4/b2 >show &&
+		grep "Initial import" show
+	)
+'
+
+test_expect_success 'sync --branch updates specific branch, no detection' '
+	test_when_finished cleanup_git &&
+	(
+		cd "$git" &&
+		git init &&
+		git p4 sync --branch=b1 //depot@2 &&
+		git p4 sync --branch=b2 //depot@2 &&
+		git p4 sync --branch=b2 &&
+		git show -s --format=%s refs/remotes/p4/b1 >show &&
+		grep "Initial import" show &&
+		git show -s --format=%s refs/remotes/p4/b2 >show &&
+		grep "change 3" show
+	)
+'
+
+# allows using the refname "p4" as a short name for p4/master
+test_expect_success 'clone creates HEAD symbolic reference' '
+	git p4 clone --dest="$git" //depot &&
+	test_when_finished cleanup_git &&
+	(
+		cd "$git" &&
+		git rev-parse --verify refs/remotes/p4/master >master &&
+		git rev-parse --verify p4 >p4 &&
+		test_cmp master p4
+	)
+'
+
+test_expect_success 'clone --branch creates HEAD symbolic reference' '
+	git p4 clone --branch=refs/remotes/p4/sb --dest="$git" //depot &&
+	test_when_finished cleanup_git &&
+	(
+		cd "$git" &&
+		git rev-parse --verify refs/remotes/p4/sb >sb &&
+		git rev-parse --verify p4 >p4 &&
+		test_cmp sb p4
 	)
 '
 
@@ -138,9 +226,11 @@ test_expect_success 'clone --use-client-spec' '
 		View: //depot/sub/... //client2/bus/...
 		EOF
 	) &&
-	P4CLIENT=client2 &&
 	test_when_finished cleanup_git &&
-	git p4 clone --dest="$git" --use-client-spec //depot/... &&
+	(
+		P4CLIENT=client2 &&
+		git p4 clone --dest="$git" --use-client-spec //depot/...
+	) &&
 	(
 		cd "$git" &&
 		test_path_is_file bus/dir/f4 &&
@@ -153,6 +243,7 @@ test_expect_success 'clone --use-client-spec' '
 		cd "$git" &&
 		git init &&
 		git config git-p4.useClientSpec true &&
+		P4CLIENT=client2 &&
 		git p4 sync //depot/... &&
 		git checkout -b master p4/master &&
 		test_path_is_file bus/dir/f4 &&
@@ -160,6 +251,31 @@ test_expect_success 'clone --use-client-spec' '
 	)
 '
 
+test_expect_success 'submit works with no p4/master' '
+	test_when_finished cleanup_git &&
+	git p4 clone --branch=b1 //depot@1,2 --destination="$git" &&
+	(
+		cd "$git" &&
+		test_commit submit-1-branch &&
+		git config git-p4.skipSubmitEdit true &&
+		git p4 submit --branch=b1
+	)
+'
+
+# The sync/rebase part post-submit will engage detect-branches
+# machinery which will not do anything in this particular test.
+test_expect_success 'submit works with two branches' '
+	test_when_finished cleanup_git &&
+	git p4 clone --branch=b1 //depot@1,2 --destination="$git" &&
+	(
+		cd "$git" &&
+		git p4 sync --branch=b2 //depot@1,3 &&
+		test_commit submit-2-branches &&
+		git config git-p4.skipSubmitEdit true &&
+		git p4 submit
+	)
+'
+
 test_expect_success 'kill p4d' '
 	kill_p4d
 '