manifest: add optional base check on remove and extend

This adds an optional, built-in checker for
guarding against patches hanging on wrong
base revisions, which is useful if a lower layer of
the manifest changes after a patch was done.

When adding a patch with a new revision using
extend-project or remove-project/project:

          C---D---E patches in project bla
         /
    A---B project bla in manifest state 1

<extend-project name="bla" revision="E" base-rev="B">

If project bla gets updated, in a new snap ID
or by a supplier or similar, to a new state:

          C---D---E patches in project bla
         /
    A---B---F---G project bla in manifest state 2

Parsing will fail because revision of bla is now G,
giving the choice to create a new patch branch
from G and updating base-rev, or keeping previous
branch for some reason and only updating base-rev.

Intended for use in a layered manifest with
hashed revisions. Named refs like branches and tags
also work fine when comparing, but will be misleading
if a branch is used as base-rev.

Change-Id: Ic6211550a7d3cc9656057f6a2087c505b40cad2b
Reviewed-on: https://gerrit-review.googlesource.com/c/git-repo/+/436777
Reviewed-by: Josip Sokcevic <sokcevic@google.com>
Tested-by: Fredrik de Groot <fredrik.de.groot@haleytek.com>
Commit-Queue: Josip Sokcevic <sokcevic@google.com>

manifest_xml.py

@@ -1445,6 +1445,7 @@ https://gerrit.googlesource.com/git-repo/+/HEAD/docs/manifest-format.md
 
         repo_hooks_project = None
         enabled_repo_hooks = None
+        failed_revision_changes = []
         for node in itertools.chain(*node_list):
             if node.nodeName == "project":
                 project = self._ParseProject(node)
@@ -1471,6 +1472,7 @@ https://gerrit.googlesource.com/git-repo/+/HEAD/docs/manifest-format.md
                     remote = self._get_remote(node)
                 dest_branch = node.getAttribute("dest-branch")
                 upstream = node.getAttribute("upstream")
+                base_revision = node.getAttribute("base-rev")
 
                 named_projects = self._projects[name]
                 if dest_path and not path and len(named_projects) > 1:
@@ -1484,6 +1486,13 @@ https://gerrit.googlesource.com/git-repo/+/HEAD/docs/manifest-format.md
                     if groups:
                         p.groups.extend(groups)
                     if revision:
+                        if base_revision:
+                            if p.revisionExpr != base_revision:
+                                failed_revision_changes.append(
+                                    "extend-project name %s mismatch base "
+                                    "%s vs revision %s"
+                                    % (name, base_revision, p.revisionExpr)
+                                )
                         p.SetRevision(revision)
 
                     if remote_name:
@@ -1558,6 +1567,7 @@ https://gerrit.googlesource.com/git-repo/+/HEAD/docs/manifest-format.md
             if node.nodeName == "remove-project":
                 name = node.getAttribute("name")
                 path = node.getAttribute("path")
+                base_revision = node.getAttribute("base-rev")
 
                 # Name or path needed.
                 if not name and not path:
@@ -1571,6 +1581,13 @@ https://gerrit.googlesource.com/git-repo/+/HEAD/docs/manifest-format.md
                 for projname, projects in list(self._projects.items()):
                     for p in projects:
                         if name == projname and not path:
+                            if base_revision:
+                                if p.revisionExpr != base_revision:
+                                    failed_revision_changes.append(
+                                        "remove-project name %s mismatch base "
+                                        "%s vs revision %s"
+                                        % (name, base_revision, p.revisionExpr)
+                                    )
                             del self._paths[p.relpath]
                             if not removed_project:
                                 del self._projects[name]
@@ -1578,6 +1595,17 @@ https://gerrit.googlesource.com/git-repo/+/HEAD/docs/manifest-format.md
                         elif path == p.relpath and (
                             name == projname or not name
                         ):
+                            if base_revision:
+                                if p.revisionExpr != base_revision:
+                                    failed_revision_changes.append(
+                                        "remove-project path %s mismatch base "
+                                        "%s vs revision %s"
+                                        % (
+                                            p.relpath,
+                                            base_revision,
+                                            p.revisionExpr,
+                                        )
+                                    )
                             self._projects[projname].remove(p)
                             del self._paths[p.relpath]
                             removed_project = p.name
@@ -1597,6 +1625,13 @@ https://gerrit.googlesource.com/git-repo/+/HEAD/docs/manifest-format.md
                         "project: %s" % node.toxml()
                     )
 
+        if failed_revision_changes:
+            raise ManifestParseError(
+                "revision base check failed, rebase patches and update "
+                "base revs for: ",
+                failed_revision_changes,
+            )
+
         # Store repo hooks project information.
         if repo_hooks_project:
             # Store a reference to the Project.