[PATCH 2/2] checkkconfigsymbols: resolve revisions before resetting the tree

[Erkan Erdem <hexvalid@gmail.com>]

The commit comparison resets the current branch to commit_a before
resolving commit_b. If the second revision is HEAD or the current branch
name, it then resolves to the first revision. For example, --diff
HEAD^..HEAD compares the parent with itself and silently misses newly
undefined symbols. The same problem affects --commit with the current
branch name.

Resolve and verify both revisions as commits before the first reset.
This keeps their meaning stable throughout the comparison and rejects
invalid endpoints before changing the working tree.

Keep lookup diagnostics separate from the resolved hashes. Use the
resolved range for --find too, since resetting also updates ORIG_HEAD.

Fixes: b1a3f243485f ("checkkconfigsymbols.py: make it Git aware")
Link: https://lore.kernel.org/20210901145212.478066-1-arielmarcovitch@gmail.com/
Assisted-by: LLM
Signed-off-by: Erkan Erdem <hexvalid@gmail.com>
---

An AI coding assistant found the issue, prepared the fix and changelog,
and ran the verification below after a request to find reproducible
functional bugs in Linux development tools.

Validation:
- Ran the actual CLI against disposable Git repositories, comparing the
  original script with the patched source. All 15 patched cases pass.
- Covered HEAD-relative ranges, branch names, hashes, tags, annotated
  tags, ambiguous branch/tag names, identical revisions, --commit,
  --find, ORIG_HEAD and invalid or non-commit endpoints.
- Checked HEAD, current branch, index and tracked file contents after
  every invocation. The patched cases preserve these values, including
  when the second revision is invalid.

 scripts/checkkconfigsymbols.py | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/scripts/checkkconfigsymbols.py b/scripts/checkkconfigsymbols.py
index 36c920e7..e0a1a631 100755
--- a/scripts/checkkconfigsymbols.py
+++ b/scripts/checkkconfigsymbols.py
@@ -150,6 +150,13 @@ def print_undefined_symbols():
             undefined_a = {}
             undefined_b = {}
 
+        commit_a = execute(["git", "rev-parse", "--verify", commit_a + "^{commit}"],
+                           stderr=None).strip()
+        commit_b = execute(["git", "rev-parse", "--verify", commit_b + "^{commit}"],
+                           stderr=None).strip()
+        if args.diff:
+            args.diff = commit_a + ".." + commit_b
+
         # get undefined items before the commit
         reset(commit_a)
         undefined_a, _ = check_symbols(args.ignore)
@@ -223,10 +230,10 @@ def red(string):
     return "\033[31m%s\033[0m" % string if COLOR else string
 
 
-def execute(cmd):
+def execute(cmd, stderr=subprocess.STDOUT):
     """Execute %cmd and return stdout.  Exit in case of error."""
     try:
-        stdout = subprocess.check_output(cmd, stderr=subprocess.STDOUT, shell=False)
+        stdout = subprocess.check_output(cmd, stderr=stderr, shell=False)
         stdout = stdout.decode(errors='replace')
     except subprocess.CalledProcessError as fail:
         exit(fail)
-- 
2.50.1 (Apple Git-155)