git.py: Fail on different branches for same repo

  doma:
    sources:
      - type: git
        url: https://github.com/xen-troops/meta-example.git
        rev: "ABCDEF"
  ...
  domu:
    sources:
      - type: git
        url: https://github.com/xen-troops/meta-example.git
        rev: "branch_A"

For doma and domu, the same GitHub repository is specified, but with
different branches.

In the case of such an erroneous YAML file, Moulin will not highlight
this error. Consequently, the user will also spend significant effort
to understand the reason for the incorrect functioning.

This patch adds an additional check to the git.py file. Now, if the
repository branches don't match, an error is displayed in the console,
and the generation of the build.ninja file is halted.

Co-Authored-By: Ihor Usyk <[email protected]>
Signed-off-by: Mykhailo Androsiuk <[email protected]>
Reviewed-by: Volodymyr Babchuk <[email protected]>

moulin/fetchers/git.py

@@ -5,6 +5,7 @@
 import os.path
 from typing import List
 import pygit2
+from moulin.yaml_helpers import YAMLProcessingError
 from moulin.yaml_wrapper import YamlValue
 from moulin.utils import create_stamp_name
 from moulin import ninja_syntax
@@ -44,7 +45,7 @@ def _guess_dirname(url: str):
     return url.split("/")[-1]
 
 
-_SEEN_REPOS = []
+_SEEN_REPOS_REV = {}
 
 
 class GitFetcher:
@@ -63,11 +64,17 @@ def gen_fetch(self):
         clone_target = self.git_dir
         checkout_stamp = create_stamp_name(self.build_dir, self.url, "checkout")
 
-        # Do not checkout repos for the second time
-        if checkout_stamp in _SEEN_REPOS:
-            return checkout_stamp
+        if checkout_stamp in _SEEN_REPOS_REV:
+            if self.git_rev != _SEEN_REPOS_REV[checkout_stamp]:
+                # Fail on occurrence of different revision for the already downloaded repository
+                raise YAMLProcessingError(f"ERROR: Repository {self.url} has two revisions '{self.git_rev}' "
+                                          f"and '{_SEEN_REPOS_REV[checkout_stamp]}'", self.conf["rev"].mark)
+            else:
+                # Do not checkout repos for the second time
+                return checkout_stamp
+
+        _SEEN_REPOS_REV[checkout_stamp] = self.git_rev
 
-        _SEEN_REPOS.append(checkout_stamp)
         self.generator.build(clone_target,
                              "git_clone",
                              variables={