[PATCH v2 2/3] git-p4: Search for parent commit on branch creation

From: Vitor Antunes <vitor.hda@gmail.com>
Date: Jan 21, 2012, 00:21 UTC
Message-ID: <1327105292-30092-3-git-send-email-vitor.hda@gmail.com>
In-Reply-To: <1327105292-30092-1-git-send-email-vitor.hda@gmail.com>

To find out which is its parent the commit of the new branch is applied sequentially to each blob of the parent branch from the newest to the oldest. The first blob which results in a zero diff is considered the parent commit. If none is found, then the commit is applied to the top of the parent branch.

A fast-import "checkpoint" call is required for each comparison because diff-tree is only able to work with blobs on disk. But most of these commits will not be part of the final imported tree, making fast-import fail. To avoid this, the temporary branches are tracked and then removed at the end of the import process.

Signed-off-by: Vitor Antunes <vitor.hda@gmail.com>
---
 contrib/fast-import/git-p4 |   30 +++++++++++++++++++++++++++++-
 1 files changed, 29 insertions(+), 1 deletions(-)

diff --git a/contrib/fast-import/git-p4 b/contrib/fast-import/git-p4
index 417d119..2e3b741 100755
--- a/contrib/fast-import/git-p4
+++ b/contrib/fast-import/git-p4
@@ -1429,6 +1429,8 @@ class P4Sync(Command, P4UserMap):
         self.cloneExclude = []
         self.useClientSpec = False
         self.clientSpecDirs = None
+        self.tempBranches = []
+        self.tempBranchLocation = "git-p4-tmp"
 
         if gitConfig("git-p4.syncFromOrigin") == "false":
             self.syncWithOrigin = False
@@ -2012,7 +2014,27 @@ class P4Sync(Command, P4UserMap):
                             parent = self.initialParents[branch]
                             del self.initialParents[branch]
 
-                        self.commit(description, filesForCommit, branch, [branchPrefix], parent)
+                        parentFound = False
+                        if len(parent) > 0:
+                            tempBranch = os.path.join(self.tempBranchLocation, "%d" % (change))
+                            if self.verbose:
+                                print "Creating temporary branch: " + tempBranch
+                            self.commit(description, filesForCommit, tempBranch, [branchPrefix])
+                            self.tempBranches.append(tempBranch)
+                            self.checkpoint()
+                            for blob in read_pipe_lines("git rev-list --reverse --no-merges %s" % parent):
+                                blob = blob.strip()
+                                if len( read_pipe("git diff-tree %s %s" % (blob, tempBranch)) ) == 0:
+                                    parentFound = True
+                                    if self.verbose:
+                                        print "Found parent of %s in commit %s" % (branch, blob)
+                                    break
+                        if parentFound:
+                            self.commit(description, filesForCommit, branch, [branchPrefix], blob)
+                        else:
+                            if self.verbose:
+                                print "Parent of %s not found. Committing into head of %s" % (branch, parent)
+                            self.commit(description, filesForCommit, branch, [branchPrefix], parent)
                 else:
                     files = self.extractFilesFromCommit(description)
                     self.commit(description, files, self.branch, self.depotPaths,
@@ -2347,6 +2369,12 @@ class P4Sync(Command, P4UserMap):
         self.gitOutput.close()
         self.gitError.close()
 
+        # Cleanup temporary branches created during import
+        if self.tempBranches != []:
+            for branch in self.tempBranches:
+                read_pipe("git update-ref -d %s" % branch)
+            os.rmdir(os.path.join(os.environ.get("GIT_DIR", ".git"), self.tempBranchLocation))
+
         return True
 
 class P4Rebase(Command):

-- 
1.7.7.rc2.14.g5e044.dirty