changelog: add hint for a file mismatch

contrib/ChangeLog:

	* gcc-changelog/git_commit.py: Suggest close file for
	'unchanged file mentioned in a ChangeLog' error.
	* gcc-changelog/test_email.py: Test it.

contrib/gcc-changelog/git_commit.py

@@ -16,6 +16,7 @@
 # along with GCC; see the file COPYING3.  If not see
 # <http://www.gnu.org/licenses/>.  */
 
+import difflib
 import os
 import re
 
@@ -576,6 +577,9 @@ class GitCommit:
         changed_files = set(cand)
         for file in sorted(mentioned_files - changed_files):
             msg = 'unchanged file mentioned in a ChangeLog'
+            candidates = difflib.get_close_matches(file, changed_files, 1)
+            if candidates:
+                msg += f' (did you mean "{candidates[0]}"?)'
             self.errors.append(Error(msg, file))
         for file in sorted(changed_files - mentioned_files):
             if not self.in_ignored_location(file):

contrib/gcc-changelog/test_email.py

@@ -113,7 +113,9 @@ class TestGccChangelog(unittest.TestCase):
         email = self.from_patch_glob('0096')
         assert email.errors
         err = email.errors[0]
-        assert err.message == 'unchanged file mentioned in a ChangeLog'
+        assert err.message == 'unchanged file mentioned in a ChangeLog (did ' \
+            'you mean "gcc/testsuite/gcc.target/aarch64/' \
+            'advsimd-intrinsics/vdot-3-1.c"?)'
         assert err.line == 'gcc/testsuite/gcc.target/aarch64/' \
                            'advsimd-intrinsics/vdot-compile-3-1.c'