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>

1 files changed, 18 insertions, 0 deletions

diff --git a/docs/manifest-format.md b/docs/manifest-format.md
index 36dae6de..cfb80164 100644
--- a/docs/manifest-format.md
+++ b/docs/manifest-format.md
@@ -107,11 +107,13 @@ following DTD:
   <!ATTLIST extend-project remote CDATA #IMPLIED>
   <!ATTLIST extend-project dest-branch CDATA #IMPLIED>
   <!ATTLIST extend-project upstream CDATA #IMPLIED>
+  <!ATTLIST extend-project base-rev CDATA #IMPLIED>
 
   <!ELEMENT remove-project EMPTY>
   <!ATTLIST remove-project name     CDATA #IMPLIED>
   <!ATTLIST remove-project path     CDATA #IMPLIED>
   <!ATTLIST remove-project optional CDATA #IMPLIED>
+  <!ATTLIST remove-project base-rev CDATA #IMPLIED>
 
   <!ELEMENT repo-hooks EMPTY>
   <!ATTLIST repo-hooks in-project CDATA #REQUIRED>
@@ -433,6 +435,14 @@ project.  Same syntax as the corresponding element of `project`.
 Attribute `upstream`: If specified, overrides the upstream of the original
 project.  Same syntax as the corresponding element of `project`.
 
+Attribute `base-rev`: If specified, adds a check against the revision
+to be extended. Manifest parse will fail and give a list of mismatch extends
+if the revisions being extended have changed since base-rev was set.
+Intended for use with layered manifests using hash revisions to prevent
+patch branches hiding newer upstream revisions. Also compares named refs
+like branches or tags but is misleading if branches are used as base-rev.
+Same syntax as the corresponding element of `project`.
+
 ### Element annotation
 
 Zero or more annotation elements may be specified as children of a
@@ -496,6 +506,14 @@ name. Logic otherwise behaves like both are specified.
 Attribute `optional`: Set to true to ignore remove-project elements with no
 matching `project` element.
 
+Attribute `base-rev`: If specified, adds a check against the revision
+to be removed. Manifest parse will fail and give a list of mismatch removes
+if the revisions being removed have changed since base-rev was set.
+Intended for use with layered manifests using hash revisions to prevent
+patch branches hiding newer upstream revisions. Also compares named refs
+like branches or tags but is misleading if branches are used as base-rev.
+Same syntax as the corresponding element of `project`.
+
 ### Element repo-hooks
 
 NB: See the [practical documentation](./repo-hooks.md) for using repo hooks.