Use CHANGE_BRANCH env.variable for build_info.git_branch

Author: st-pasha

ci/ext.py

@@ -450,8 +450,11 @@ def generate_build_info(mode=None, strict=False):
     # get the date of the commit (HEAD), as a Unix timestamp
     git_date = shell_cmd(["git", "show", "-s", "--format=%ct", "HEAD"],
                          strict=strict)
-    git_branch = shell_cmd(["git", "rev-parse", "--abbrev-ref", "HEAD"],
-                           strict=strict)
+    if "CHANGE_BRANCH" in os.environ:
+        git_branch = os.environ["CHANGE_BRANCH"]
+    else:
+        git_branch = shell_cmd(["git", "rev-parse", "--abbrev-ref", "HEAD"],
+                               strict=strict)
     git_diff = shell_cmd(["git", "diff", "HEAD", "--stat", "--no-color"],
                          strict=strict)
     # Reformat the `git_date` as a UTC time string

docs/api/dt/build_info.rst

@@ -43,8 +43,9 @@
 
     .. xparam:: .git_branch: str
 
-        Name of the git branch from where the build was made, as
-        obtained from ``git rev-parse --abbrev-ref HEAD``.
+        Name of the git branch from where the build was made. This will
+        be obtained from environment variable ``CHANGE_BRANCH`` if defined,
+        or from command ``git rev-parse --abbrev-ref HEAD`` otherwise.
 
 
     .. xparam:: .git_date: str