3 files changed, 64 insertions, 4 deletions

diff --git a/docs/manifest-format.md b/docs/manifest-format.md
index bcdf5a8e..edcb28cb 100644
--- a/docs/manifest-format.md
+++ b/docs/manifest-format.md
@@ -125,8 +125,9 @@ following DTD:
   <!ATTLIST contactinfo bugurl  CDATA #REQUIRED>
 
   <!ELEMENT include EMPTY>
-  <!ATTLIST include name   CDATA #REQUIRED>
-  <!ATTLIST include groups CDATA #IMPLIED>
+  <!ATTLIST include name     CDATA #REQUIRED>
+  <!ATTLIST include groups   CDATA #IMPLIED>
+  <!ATTLIST include revision CDATA #IMPLIED>
 ]>
 ```
 
@@ -553,6 +554,9 @@ in the included manifest belong. This appends and recurses, meaning
 all projects in included manifests carry all parent include groups.
 Same syntax as the corresponding element of `project`.
 
+Attribute `revision`: Name of a Git branch (e.g. `main` or `refs/heads/main`)
+default to which all projects in the included manifest belong.
+
 ## Local Manifests {#local-manifests}
 
 Additional remotes and projects may be added through local manifest
diff --git a/manifest_xml.py b/manifest_xml.py
index 9603906f..14b03a30 100644
--- a/manifest_xml.py
+++ b/manifest_xml.py
@@ -1233,7 +1233,12 @@ https://gerrit.googlesource.com/git-repo/+/HEAD/docs/manifest-format.md
                     )
 
     def _ParseManifestXml(
-        self, path, include_root, parent_groups="", restrict_includes=True
+        self,
+        path,
+        include_root,
+        parent_groups="",
+        restrict_includes=True,
+        parent_node=None,
     ):
         """Parse a manifest XML and return the computed nodes.
 
@@ -1243,6 +1248,8 @@ https://gerrit.googlesource.com/git-repo/+/HEAD/docs/manifest-format.md
             parent_groups: The groups to apply to this projects.
             restrict_includes: Whether to constrain the "name" attribute of
                 includes.
+            parent_node: The parent include node, to apply attribute to this
+                projects.
 
         Returns:
             List of XML nodes.
@@ -1288,7 +1295,9 @@ https://gerrit.googlesource.com/git-repo/+/HEAD/docs/manifest-format.md
                     )
                 try:
                     nodes.extend(
-                        self._ParseManifestXml(fp, include_root, include_groups)
+                        self._ParseManifestXml(
+                            fp, include_root, include_groups, parent_node=node
+                        )
                     )
                 # should isolate this to the exact exception, but that's
                 # tricky.  actual parsing implementation may vary.
@@ -1311,6 +1320,14 @@ https://gerrit.googlesource.com/git-repo/+/HEAD/docs/manifest-format.md
                             node.getAttribute("groups") + "," + nodeGroups
                         )
                     node.setAttribute("groups", nodeGroups)
+                if (
+                    parent_node
+                    and node.nodeName == "project"
+                    and not node.hasAttribute("revision")
+                ):
+                    node.setAttribute(
+                        "revision", parent_node.getAttribute("revision")
+                    )
                 nodes.append(node)
         return nodes
 
diff --git a/tests/test_manifest_xml.py b/tests/test_manifest_xml.py
index 648acde8..ef511055 100644
--- a/tests/test_manifest_xml.py
+++ b/tests/test_manifest_xml.py
@@ -389,6 +389,45 @@ class XmlManifestTests(ManifestParseTestCase):
 class IncludeElementTests(ManifestParseTestCase):
     """Tests for <include>."""
 
+    def test_revision_default(self):
+        """Check handling of revision attribute."""
+        root_m = os.path.join(self.manifest_dir, "root.xml")
+        with open(root_m, "w") as fp:
+            fp.write(
+                """
+<manifest>
+  <remote name="test-remote" fetch="http://localhost" />
+  <default remote="test-remote" revision="refs/heads/main" />
+  <include name="stable.xml" revision="stable-branch" />
+  <project name="root-name1" path="root-path1" />
+  <project name="root-name2" path="root-path2" />
+</manifest>
+"""
+            )
+        with open(os.path.join(self.manifest_dir, "stable.xml"), "w") as fp:
+            fp.write(
+                """
+<manifest>
+  <project name="stable-name1" path="stable-path1" />
+  <project name="stable-name2" path="stable-path2" revision="stable-branch2" />
+</manifest>
+"""
+            )
+        include_m = manifest_xml.XmlManifest(self.repodir, root_m)
+        for proj in include_m.projects:
+            if proj.name == "root-name1":
+                # Check include revision not set on root level proj.
+                self.assertNotEqual("stable-branch", proj.revisionExpr)
+            if proj.name == "root-name2":
+                # Check root proj revision not removed.
+                self.assertEqual("refs/heads/main", proj.revisionExpr)
+            if proj.name == "stable-name1":
+                # Check stable proj has inherited revision include node.
+                self.assertEqual("stable-branch", proj.revisionExpr)
+            if proj.name == "stable-name2":
+                # Check stable proj revision can override include node.
+                self.assertEqual("stable-branch2", proj.revisionExpr)
+
     def test_group_levels(self):
         root_m = os.path.join(self.manifest_dir, "root.xml")
         with open(root_m, "w") as fp: