Commit log message typos and spell mistakes

@@ -737,6 +737,15 @@ color.ui::
 	terminal. When more specific variables of color.* are set, they always
 	take precedence over this setting. Defaults to false.
 
+commit.spell::
+	A boolean to enable/disable running of the spell checker on commit
+	log message. Defaults to false.
+
+commit.spellcommand::
+	Shell command to run as the spell checker. First argument given to
+	the command is the name of the file containing the commit log message.
+	Defaults to `ispell`.  See 'ispell(1)'.
+
 commit.status::
 	A boolean to enable/disable inclusion of status information in the
 	commit message template when using an editor to prepare the commit

@@ -120,6 +120,14 @@ OPTIONS
 	Add Signed-off-by line by the committer at the end of the commit
 	log message.
 
+--spell::
+	Run the spell checker on commit log message. This overrides the
+	`commit.spell` configuration variable.
+
+--no-spell::
+	Do not run the spell checker on commit log message. This overrides the
+	`commit.spell` configuration variable.
+
 -n::
 --no-verify::
 	This option bypasses the pre-commit and commit-msg hooks.

@@ -66,7 +66,8 @@ static char *edit_message, *use_message;
 static char *author_name, *author_email, *author_date;
 static int all, edit_flag, also, interactive, only, amend, signoff;
 static int quiet, verbose, no_verify, allow_empty, dry_run, renew_authorship;
-static int no_post_rewrite;
+static int no_post_rewrite, spell_check;
+static const char *spell_command = (const char*)"ispell";
 static char *untracked_files_arg, *force_date;
 /*
  * The default commit message cleanup mode will remove the lines

@@ -93,6 +94,11 @@ static enum {
 	STATUS_FORMAT_PORCELAIN,
 } status_format = STATUS_FORMAT_LONG;
 
+static inline int have_terminal(void)
+{
+	return (isatty(0) && isatty(1) && isatty(2));
+}
+
 static int opt_parse_m(const struct option *opt, const char *arg, int unset)
 {
 	struct strbuf *buf = opt->value;

@@ -118,6 +124,7 @@ static struct option builtin_commit_options[] = {
 	OPT_STRING('C', "reuse-message", &use_message, "COMMIT", "reuse message from specified commit"),
 	OPT_BOOLEAN(0, "reset-author", &renew_authorship, "the commit is authored by me now (used with -C-c/--amend)"),
 	OPT_BOOLEAN('s', "signoff", &signoff, "add Signed-off-by:"),
+	OPT_BOOLEAN(0, "spell", &spell_check, "run spell checker on commit message"),
 	OPT_FILENAME('t', "template", &template_file, "use specified template file"),
 	OPT_BOOLEAN('e', "edit", &edit_flag, "force edit of commit"),
 	OPT_STRING(0, "cleanup", &cleanup_arg, "default", "how to strip spaces and #comments from message"),

@@ -525,6 +532,21 @@ static int ends_rfc2822_footer(struct strbuf *sb)
 	return 1;
 }
 
+static int spell_checker(const char *commit_editmsg)
+{
+	const char *terminal = getenv("TERM");
+	int terminal_is_dumb = !terminal || !strcmp(terminal, "dumb");
+
+	if (terminal_is_dumb || !have_terminal()) {
+		error("No Terminal, can not run spell checker");
+		return 0;
+	}
+
+	const char *args[] = { spell_command, commit_editmsg, NULL };
+
+	return run_command_v_opt(args, RUN_USING_SHELL);
+}
+
 static int prepare_to_commit(const char *index_file, const char *prefix,
 			     struct wt_status *s)
 {

@@ -726,6 +748,9 @@ static int prepare_to_commit(const char *index_file, const char *prefix,
 		}
 	}
 
+	if (spell_check && spell_checker(git_path(commit_editmsg)))
+		return 0;
+
 	if (!no_verify &&
 	    run_hook(index_file, "commit-msg", git_path(commit_editmsg), NULL)) {
 		return 0;

@@ -1154,6 +1179,12 @@ static int git_commit_config(const char *k, const char *v, void *cb)
 
 	if (!strcmp(k, "commit.template"))
 		return git_config_pathname(&template_file, k, v);
+	if (!strcmp(k, "commit.spell")) {
+		spell_check = git_config_bool(k, v);
+		return 0;
+	}
+	if (!strcmp(k, "commit.spellcommand"))
+		return git_config_string(&spell_command, k, v);
 	if (!strcmp(k, "commit.status")) {
 		include_status = git_config_bool(k, v);
 		return 0;