expose HEAD's commit message

Add two new new message fields to the gitstatusd's reply and
expose them in bash and zsh bindings:

- VCS_STATUS_COMMIT_ENCODING:
  Encoding of the HEAD's commit message. Empty value means UTF-8.
- VCS_STATUS_COMMIT_SUMMARY:
  The first paragraph of the HEAD's commit message as one line.

Commit summary is truncated to 256 bytes. This can be overridden
with --max-commit-summary-length/-z.

Note that truncation may result in invalid UTF-8.

Messages in exotic may not work because of SafePrint() in
gitstatusd. This can be fixed.

gitstatus.plugin.sh

@@ -300,6 +300,8 @@ function gitstatus_stop() {
 #   VCS_STATUS_WORKDIR              Git repo working directory. Not empty.
 #   VCS_STATUS_COMMIT               Commit hash that HEAD is pointing to. Either 40 hex digits or
 #                                   empty if there is no HEAD (empty repo).
+#   VCS_STATUS_COMMIT_ENCODING      Encoding of the HEAD's commit message. Empty value means UTF-8.
+#   VCS_STATUS_COMMIT_SUMMARY       The first paragraph of the HEAD's commit message as one line.
 #   VCS_STATUS_LOCAL_BRANCH         Local branch name or empty if not on a branch.
 #   VCS_STATUS_REMOTE_NAME          The remote name, e.g. "upstream" or "origin".
 #   VCS_STATUS_REMOTE_BRANCH        Upstream branch name. Can be empty.
@@ -403,6 +405,8 @@ function gitstatus_query() {
     VCS_STATUS_PUSH_COMMITS_BEHIND="${resp[24]:-0}"
     VCS_STATUS_NUM_SKIP_WORKTREE="${resp[25]:-0}"
     VCS_STATUS_NUM_ASSUME_UNCHANGED="${resp[26]:-0}"
+    VCS_STATUS_COMMIT_ENCODING="${resp[27]-}"
+    VCS_STATUS_COMMIT_SUMMARY="${resp[28]-}"
     VCS_STATUS_HAS_STAGED=$((VCS_STATUS_NUM_STAGED > 0))
     if (( _GITSTATUS_DIRTY_MAX_INDEX_SIZE >= 0 &&
           VCS_STATUS_INDEX_SIZE > _GITSTATUS_DIRTY_MAX_INDEX_SIZE_ )); then
@@ -445,6 +449,8 @@ function gitstatus_query() {
     unset VCS_STATUS_PUSH_COMMITS_BEHIND
     unset VCS_STATUS_NUM_SKIP_WORKTREE
     unset VCS_STATUS_NUM_ASSUME_UNCHANGED
+    unset VCS_STATUS_COMMIT_ENCODING
+    unset VCS_STATUS_COMMIT_SUMMARY
   fi
 }
 

gitstatus.plugin.zsh

@@ -15,6 +15,8 @@
 #   VCS_STATUS_COMMIT=c000eddcff0fb38df2d0137efe24d9d2d900f209
 #   VCS_STATUS_COMMITS_AHEAD=0
 #   VCS_STATUS_COMMITS_BEHIND=0
+#   VCS_STATUS_COMMIT_ENCODING=''
+#   VCS_STATUS_COMMIT_SUMMARY='pull upstream changes from gitstatus'
 #   VCS_STATUS_HAS_CONFLICTED=0
 #   VCS_STATUS_HAS_STAGED=0
 #   VCS_STATUS_HAS_UNSTAGED=1
@@ -88,6 +90,8 @@ typeset -g _gitstatus_plugin_dir"${1:-}"="${${(%):-%x}:A:h}"
 #   VCS_STATUS_WORKDIR              Git repo working directory. Not empty.
 #   VCS_STATUS_COMMIT               Commit hash that HEAD is pointing to. Either 40 hex digits or
 #                                   empty if there is no HEAD (empty repo).
+#   VCS_STATUS_COMMIT_ENCODING      Encoding of the HEAD's commit message. Empty value means UTF-8.
+#   VCS_STATUS_COMMIT_SUMMARY       The first paragraph of the HEAD's commit message as one line.
 #   VCS_STATUS_LOCAL_BRANCH         Local branch name or empty if not on a branch.
 #   VCS_STATUS_REMOTE_NAME          The remote name, e.g. "upstream" or "origin".
 #   VCS_STATUS_REMOTE_BRANCH        Upstream branch name. Can be empty.
@@ -329,7 +333,9 @@ function _gitstatus_process_response"${1:-}"() {
           VCS_STATUS_PUSH_COMMITS_AHEAD   \
           VCS_STATUS_PUSH_COMMITS_BEHIND  \
           VCS_STATUS_NUM_SKIP_WORKTREE    \
-          VCS_STATUS_NUM_ASSUME_UNCHANGED in "${(@)resp[3,27]}"; do
+          VCS_STATUS_NUM_ASSUME_UNCHANGED \
+          VCS_STATUS_COMMIT_ENCODING      \
+          VCS_STATUS_COMMIT_SUMMARY in "${(@)resp[3,29]}"; do
       done
       typeset -gi VCS_STATUS_{INDEX_SIZE,NUM_STAGED,NUM_UNSTAGED,NUM_CONFLICTED,NUM_UNTRACKED,COMMITS_AHEAD,COMMITS_BEHIND,STASHES,NUM_UNSTAGED_DELETED,NUM_STAGED_NEW,NUM_STAGED_DELETED,PUSH_COMMITS_AHEAD,PUSH_COMMITS_BEHIND,NUM_SKIP_WORKTREE,NUM_ASSUME_UNCHANGED}
       typeset -gi VCS_STATUS_HAS_STAGED=$((VCS_STATUS_NUM_STAGED > 0))

src/git.cc

@@ -239,4 +239,12 @@ PushRemotePtr GetPushRemote(git_repository* repo, const git_reference* local) {
   return PushRemotePtr(res.release());
 }
 
+CommitMessage GetCommitMessage(git_repository* repo, const git_oid& id) {
+  git_commit* commit;
+  VERIFY(!git_commit_lookup(&commit, repo, &id)) << GitError();
+  ON_SCOPE_EXIT(=) { git_commit_free(commit); };
+  return {.encoding = git_commit_message_encoding(commit) ?: "",
+          .summary = git_commit_summary(commit) ?: ""};
+}
+
 }  // namespace gitstatus

src/git.h

@@ -48,6 +48,15 @@ git_reference* Head(git_repository* repo);
 // Returns the name of the local branch, or an empty string.
 const char* LocalBranchName(const git_reference* ref);
 
+struct CommitMessage {
+  // Can be empty, meaning "UTF-8".
+  std::string encoding;
+  // The first paragraph of the commit's message as a one-liner.
+  std::string summary;
+};
+
+CommitMessage GetCommitMessage(git_repository* repo, const git_oid& id);
+
 struct Remote {
   // Tip of the remote branch.
   git_reference* ref;

src/gitstatus.cc

@@ -41,6 +41,10 @@ namespace {
 
 using namespace std::string_literals;
 
+void Truncate(std::string& s, size_t max_len) {
+  if (s.size() > max_len) s.resize(max_len);
+}
+
 void ProcessRequest(const Options& opts, RepoCache& cache, Request req) {
   Timer timer;
   ON_SCOPE_EXIT(&) { timer.Report("request"); };
@@ -167,6 +171,11 @@ void ProcessRequest(const Options& opts, RepoCache& cache, Request req) {
   // The number of files in the index with assume-unchanged bit set.
   resp.Print(stats.num_assume_unchanged);
 
+  CommitMessage msg = head_target ? GetCommitMessage(repo->repo(), *head_target) : CommitMessage();
+  Truncate(msg.summary, opts.max_commit_summary_length);
+  resp.Print(msg.encoding);
+  resp.Print(msg.summary);
+
   resp.Dump("with git status");
 }
 

src/options.cc

@@ -53,6 +53,12 @@ long ParseInt(const char* s) {
   return res;
 }
 
+size_t ParseSizeT(const char* s) {
+  static_assert(sizeof(long) <= sizeof(size_t));
+  long res = ParseLong(s);
+  return res >= 0 ? res : -1;
+}
+
 void PrintUsage() {
   std::cout << "Usage: gitstatusd [OPTION]...\n"
             << "Print machine-readable status of the git repos for directores in stdin.\n"
@@ -81,12 +87,18 @@ void PrintUsage() {
             << "   repo that's been closed is much slower than for a repo that hasn't been.\n"
             << "   Negative value means infinity.\n"
             << "\n"
+            << "  -z, --max-commit-summary-length=NUM [default=256]\n"
+            << "   Truncate commit summary if it's longer than this many bytes.\n"
+            << "\n"
             << "  -s, --max-num-staged=NUM [default=1]\n"
             << "   Report at most this many staged changes; negative value means infinity.\n"
             << "\n"
             << "  -u, --max-num-unstaged=NUM [default=1]\n"
             << "   Report at most this many unstaged changes; negative value means infinity.\n"
             << "\n"
+            << "  -c, --max-num-conflicted=NUM [default=1]\n"
+            << "   Report at most this many conflicted changes; negative value means infinity.\n"
+            << "\n"
             << "  -d, --max-num-untracked=NUM [default=1]\n"
             << "   Report at most this many untracked files; negative value means infinity.\n"
             << "\n"
@@ -170,6 +182,8 @@ void PrintUsage() {
             << "    25. Number of commits the current branch is behind push remote.\n"
             << "    26. Number of files in the index with skip-worktree bit set.\n"
             << "    27. Number of files in the index with assume-unchanged bit set.\n"
+            << "    28. Encoding of the HEAD's commit message. Empty value means UTF-8.\n"
+            << "    29. The first paragraph of the HEAD's commit message as one line.\n"
             << "\n"
             << "Note: Renamed files are reported as deleted plus new.\n"
             << "\n"
@@ -212,6 +226,8 @@ void PrintUsage() {
             << "    '0'\n"
             << "    '0'\n"
             << "    '0'\n"
+            << "    ''\n"
+            << "    'add a build server for darwin-arm64'\n"
             << "\n"
             << "EXIT STATUS\n"
             << "\n"
@@ -245,6 +261,7 @@ Options ParseOptions(int argc, char** argv) {
                                 {"num-threads", required_argument, nullptr, 't'},
                                 {"log-level", required_argument, nullptr, 'v'},
                                 {"repo-ttl-seconds", required_argument, nullptr, 'r'},
+                                {"max-commit-summary-length", required_argument, nullptr, 'z'},
                                 {"max-num-staged", required_argument, nullptr, 's'},
                                 {"max-num-unstaged", required_argument, nullptr, 'u'},
                                 {"max-num-conflicted", required_argument, nullptr, 'c'},
@@ -257,7 +274,7 @@ Options ParseOptions(int argc, char** argv) {
                                 {}};
   Options res;
   while (true) {
-    switch (getopt_long(argc, argv, "hVG:l:p:t:v:r:s:u:c:d:m:eUWD", opts, nullptr)) {
+    switch (getopt_long(argc, argv, "hVG:l:p:t:v:r:z:s:u:c:d:m:eUWD", opts, nullptr)) {
       case -1:
         if (optind != argc) {
           std::cerr << "unexpected positional argument: " << argv[optind] << std::endl;
@@ -306,20 +323,23 @@ Options ParseOptions(int argc, char** argv) {
         res.num_threads = n;
         break;
       }
+      case 'z':
+        res.max_commit_summary_length = ParseSizeT(optarg);
+        break;
       case 's':
-        res.max_num_staged = ParseLong(optarg);
+        res.max_num_staged = ParseSizeT(optarg);
         break;
       case 'u':
-        res.max_num_unstaged = ParseLong(optarg);
+        res.max_num_unstaged = ParseSizeT(optarg);
         break;
       case 'c':
-        res.max_num_conflicted = ParseLong(optarg);
+        res.max_num_conflicted = ParseSizeT(optarg);
         break;
       case 'd':
-        res.max_num_untracked = ParseLong(optarg);
+        res.max_num_untracked = ParseSizeT(optarg);
         break;
       case 'm':
-        res.dirty_max_index_size = ParseLong(optarg);
+        res.dirty_max_index_size = ParseSizeT(optarg);
         break;
       case 'e':
         res.recurse_untracked_dirs = true;

src/options.h

@@ -27,6 +27,8 @@
 namespace gitstatus {
 
 struct Limits {
+  // Truncate commit summary if it's longer than this many bytes.
+  size_t max_commit_summary_length = 256;
   // Report at most this many staged changes.
   size_t max_num_staged = 1;
   // Report at most this many unstaged changes.