Add Git hooks to check filenames listed in the commit message

See <https://lists.gnu.org/archive/html/emacs-devel/2023-04/msg00274.html>.

* build-aux/git-hooks/commit-msg-files.awk:
* build-aux/git-hooks/post-commit:
* build-aux/git-hooks/pre-push: New files...
* autogen.sh: ... add them.

1 files changed, 113 insertions, 0 deletions

diff --git a/build-aux/git-hooks/commit-msg-files.awk b/build-aux/git-hooks/commit-msg-files.awk
new file mode 100644
index 00000000000..3856e474d3e
--- /dev/null
+++ b/build-aux/git-hooks/commit-msg-files.awk
@@ -0,0 +1,113 @@
+# Check the file list of GNU Emacs change log entries for each commit SHA.
+
+# Copyright 2023 Free Software Foundation, Inc.
+
+# This file is part of GNU Emacs.
+
+# GNU Emacs is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+
+# GNU Emacs is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+
+# You should have received a copy of the GNU General Public License
+# along with GNU Emacs.  If not, see <https://www.gnu.org/licenses/>.
+
+### Commentary:
+
+# This script accepts a list of (unabbreviated) Git commit SHAs, and
+# will then iterate over them to check that any files mentioned in the
+# commit message are actually present in the commit's diff.  If not,
+# it will print out the incorrect file names and return 1.
+
+# You can also pass "-v reason=pre-push", which will add more-verbose
+# output, indicating the abbreviated commit SHA and first line of the
+# commit message for any improper commits.
+
+### Code:
+
+function get_commit_changes(commit_sha, changes,    cmd, i, j, len, \
+                            bits, filename) {
+  # Collect all the files touched in the specified commit.
+  cmd = ("git log -1 --name-status --format= " commit_sha)
+  while ((cmd | getline) > 0) {
+    for (i = 2; i <= NF; i++) {
+      len = split($i, bits, "/")
+      for (j = 1; j <= len; j++) {
+        if (j == 1)
+          filename = bits[j]
+        else
+          filename = filename "/" bits[j]
+        changes[filename] = 1
+      }
+    }
+  }
+  close(cmd)
+}
+
+function check_commit_msg_files(commit_sha, verbose,    changes, good, \
+                                cmd, msg, filenames_str, filenames, i) {
+  get_commit_changes(commit_sha, changes)
+  good = 1
+
+  cmd = ("git log -1 --format=%B " commit_sha)
+  while ((cmd | getline) > 0) {
+    if (verbose && ! msg)
+      msg = $0
+
+    # Find lines that reference files.  We look at any line starting
+    # with "*" (possibly prefixed by "; ") where the file part starts
+    # with an alphanumeric character.  The file part ends if we
+    # encounter any of the following characters: [ ( < { :
+    if (/^(; )?\*[ \t]+[[:alnum:]]/ && match($0, /[[:alnum:]][^[(<{:]*/)) {
+      # There might be multiple files listed on this line, separated
+      # by spaces (and possibly a comma).  Iterate over each of them.
+      split(substr($0, RSTART, RLENGTH), filenames, ",?([[:blank:]]+|$)")
+
+      for (i in filenames) {
+        # Remove trailing slashes from any directory entries.
+        sub(/\/$/, "", filenames[i])
+
+        if (length(filenames[i]) && ! (filenames[i] in changes)) {
+          if (good) {
+            # Print a header describing the error.
+            if (verbose)
+              printf("In commit %s \"%s\"...\n", substr(commit_sha, 1, 10), msg)
+            printf("Files listed in commit message, but not in diff:\n")
+          }
+          printf("  %s\n", filenames[i])
+          good = 0
+        }
+      }
+    }
+  }
+  close(cmd)
+
+  return good
+}
+
+BEGIN {
+  if (reason == "pre-push")
+    verbose = 1
+}
+
+/^[a-z0-9]{40}$/ {
+  if (! check_commit_msg_files($0, verbose)) {
+    status = 1
+  }
+}
+
+END {
+  if (status != 0) {
+    if (reason == "pre-push")
+      error_msg = "Push aborted"
+    else
+      error_msg = "Bad commit message"
+    printf("%s; please see the file 'CONTRIBUTE'\n", error_msg)
+  }
+  exit status
+}