Add 'rebase="false"' attribute to the <project/> XML.

This new attribute can prevent 'repo sync' from automatically rebasing.

I hit a situation in where one of the git repositories I was tracking
was actually an external repository that I wanted to pull commits
into and merge myself. (NOT rebase, since that would lose the merge
history.) In this case, I'm not using 'repo upload', I'm manually
managing the merges to and from this repository.

Everything was going great until I typed 'repo sync' and it rebased
my manually-merged tree. Hence the option to skip it.

Change-Id: I965e0dd1acb87f4a56752ebedc7e2de1c502dbf8

manifest_xml.py

@@ -498,6 +498,12 @@ class XmlManifest(object):
             "project %s path cannot be absolute in %s" % \
             (name, self.manifestFile)
 
+    rebase = node.getAttribute('rebase')
+    if not rebase:
+      rebase = True
+    else:
+      rebase = rebase.lower() in ("yes", "true", "1")
+
     if self.IsMirror:
       relpath = None
       worktree = None
@@ -513,7 +519,8 @@ class XmlManifest(object):
                       worktree = worktree,
                       relpath = path,
                       revisionExpr = revisionExpr,
-                      revisionId = None)
+                      revisionId = None,
+                      rebase = rebase)
 
     for n in node.childNodes:
       if n.nodeName == 'copyfile':

project.py

@@ -503,7 +503,8 @@ class Project(object):
                worktree,
                relpath,
                revisionExpr,
-               revisionId):
+               revisionId,
+               rebase = True):
     self.manifest = manifest
     self.name = name
     self.remote = remote
@@ -522,6 +523,8 @@ class Project(object):
     else:
       self.revisionId = revisionId
 
+    self.rebase = rebase
+
     self.snapshots = {}
     self.copyfiles = []
     self.config = GitConfig.ForRepository(
@@ -1096,7 +1099,7 @@ class Project(object):
     branch.merge = self.revisionExpr
     branch.Save()
 
-    if cnt_mine > 0:
+    if cnt_mine > 0 and self.rebase:
       def _dorebase():
         self._Rebase(upstream = '%s^1' % last_mine, onto = revid)
         self._CopyFiles()