[PATCH] help: prompt user to run corrected command on typo

[calicomills <jishnuck26@gmail.com>]

From 0dc9e5c4593611b75e7003e8fdbea9370524c05b Mon Sep 17 00:00:00 2001
From: calicomills <jishnuck26@gmail.com>
Date: Thu, 18 Jun 2026 19:47:12 +0530
Subject: [PATCH] help: prompt user to run corrected command on typo

When a user mistypes a git command and there is exactly one similar
command, git currently prints a suggestion but exits, requiring the
user to retype the corrected command manually.

Instead, when stdin and stderr are both connected to a terminal and
there is a single best match, prompt the user with:

  Did you mean 'git checkout neo'? [y/N]

The full corrected invocation (command + original arguments) is shown
in the prompt so the user knows exactly what will run. Answering 'y'
re-executes git with the corrected command and all original arguments.
Answering anything else exits as before.

When there are multiple similarly-named commands, or when running
non-interactively (scripts, pipes), the original behaviour of printing
the suggestion list and exiting is preserved.

The help_unknown_cmd() signature is updated to accept the full args
vector so the prompt can include the original arguments alongside the
corrected command name.

Add tests to t9003 covering:
- non-interactive single match: falls back to suggestion list
- non-interactive multiple matches: falls back to suggestion list
- interactive single match, 'y': corrected command runs (TTY prereq)
- interactive single match, 'n': exits cleanly (TTY prereq)

Signed-off-by: calicomills <jishnuck26@gmail.com>
---
 builtin/help.c              |  2 +-
 git.c                       |  2 +-
 help.c                      | 40 ++++++++++++++++++++++------
 help.h                      |  3 ++-
 t/t9003-help-autocorrect.sh | 53 +++++++++++++++++++++++++++++++++++++
 5 files changed, 89 insertions(+), 11 deletions(-)

diff --git a/builtin/help.c b/builtin/help.c
index a140339999..b17e61ccc8 100644
--- a/builtin/help.c
+++ b/builtin/help.c
@@ -618,7 +618,7 @@ static char *check_git_cmd(const char *cmd)
 	}
 
 	if (exclude_guides)
-		return help_unknown_cmd(cmd);
+		return help_unknown_cmd(cmd, NULL);
 
 	return xstrdup(cmd);
 }
diff --git a/git.c b/git.c
index 36f08891ef..d379cc85bb 100644
--- a/git.c
+++ b/git.c
@@ -994,7 +994,7 @@ int cmd_main(int argc, const char **argv)
 			exit(1);
 		}
 		if (!done_help) {
-			char *assumed = help_unknown_cmd(cmd);
+			char *assumed = help_unknown_cmd(cmd, &args);
 			strvec_replace(&args, 0, assumed);
 			free(assumed);
 			cmd = args.v[0];
diff --git a/help.c b/help.c
index 46241492ce..30f32a7206 100644
--- a/help.c
+++ b/help.c
@@ -641,7 +641,7 @@ static const char bad_interpreter_advice[] =
 	N_("'%s' appears to be a git command, but we were not\n"
 	"able to execute it. Maybe git-%s is broken?");
 
-char *help_unknown_cmd(const char *cmd)
+char *help_unknown_cmd(const char *cmd, const struct strvec *args)
 {
 	struct help_unknown_cmd_config cfg = { 0 };
 	int i, n, best_similarity = 0;
@@ -762,13 +762,37 @@ char *help_unknown_cmd(const char *cmd)
 	fprintf_ln(stderr, _("git: '%s' is not a git command. See 'git --help'."), cmd);
 
 	if (SIMILAR_ENOUGH(best_similarity)) {
-		fprintf_ln(stderr,
-			   Q_("\nThe most similar command is",
-			      "\nThe most similar commands are",
-			   n));
-
-		for (i = 0; i < n; i++)
-			fprintf(stderr, "\t%s\n", main_cmds.names[i]->name);
+		if (n == 1 && isatty(0) && isatty(2)) {
+			char *answer;
+			struct strbuf msg = STRBUF_INIT;
+			struct strbuf full_cmd = STRBUF_INIT;
+			strbuf_addstr(&full_cmd, main_cmds.names[0]->name);
+			if (args) {
+				for (size_t j = 1; j < args->nr; j++) {
+					strbuf_addch(&full_cmd, ' ');
+					strbuf_addstr(&full_cmd, args->v[j]);
+				}
+			}
+			strbuf_addf(&msg, _("\nDid you mean 'git %s'? [y/N] "),
+				    full_cmd.buf);
+			strbuf_release(&full_cmd);
+			answer = git_prompt(msg.buf, PROMPT_ECHO);
+			strbuf_release(&msg);
+			if (starts_with(answer, "y") || starts_with(answer, "Y")) {
+				char *assumed = xstrdup(main_cmds.names[0]->name);
+				cmdnames_release(&cfg.aliases);
+				cmdnames_release(&main_cmds);
+				cmdnames_release(&other_cmds);
+				return assumed;
+			}
+		} else {
+			fprintf_ln(stderr,
+				   Q_("\nThe most similar command is",
+				      "\nThe most similar commands are",
+				   n));
+			for (i = 0; i < n; i++)
+				fprintf(stderr, "\t%s\n", main_cmds.names[i]->name);
+		}
 	}
 
 	exit(1);
diff --git a/help.h b/help.h
index c54bf0977d..a8c465b3df 100644
--- a/help.h
+++ b/help.h
@@ -32,7 +32,8 @@ void list_all_other_cmds(struct string_list *list);
 void list_cmds_by_category(struct string_list *list,
 			   const char *category);
 void list_cmds_by_config(struct string_list *list);
-char *help_unknown_cmd(const char *cmd);
+#include "strvec.h"
+char *help_unknown_cmd(const char *cmd, const struct strvec *args);
 void load_command_list(const char *prefix,
 		       struct cmdnames *main_cmds,
 		       struct cmdnames *other_cmds);
diff --git a/t/t9003-help-autocorrect.sh b/t/t9003-help-autocorrect.sh
index 8da318d2b5..6fe2da1595 100755
--- a/t/t9003-help-autocorrect.sh
+++ b/t/t9003-help-autocorrect.sh
@@ -70,4 +70,57 @@ test_expect_success 'autocorrect works in work tree created from bare repo' '
 	git -C worktree -c help.autocorrect=immediate status
 '
 
+# Default behaviour (no help.autocorrect set): when there is exactly one
+# similar command but the session is non-interactive, fall back to printing
+# the suggestion list and exiting rather than showing a prompt.
+test_expect_success 'default: single match non-interactive shows suggestion and fails' '
+	test_might_fail git config --unset help.autocorrect &&
+
+	test_must_fail git lfg 2>actual &&
+	grep "most similar command" actual &&
+	grep "lgf" actual
+'
+
+test_expect_success 'default: multiple matches non-interactive shows list and fails' '
+	test_might_fail git config --unset help.autocorrect &&
+
+	test_must_fail git com 2>actual &&
+	grep "most similar commands" actual &&
+	grep "commit" actual
+'
+
+# Interactive prompt tests require a real TTY.  On macOS the TTY prereq is
+# skipped due to IO::Pty reliability issues; these tests run on Linux CI.
+test_expect_success TTY 'default: single match interactive, answer y runs command' '
+	git config --unset help.autocorrect &&
+
+	write_script git-typotest <<-\EOF &&
+		echo typotest-ran
+	EOF
+	PATH="$PATH:." export PATH &&
+
+	# Feed "y" to /dev/tty via a wrapper that answers the prompt
+	write_script answer-prompt <<-\EOF &&
+		# Write the answer to the controlling terminal
+		printf "y\n" >/dev/tty
+		exec "$@"
+	EOF
+
+	test_terminal ./answer-prompt git typotest 2>err >out &&
+	grep "typotest-ran" out &&
+	grep "Did you mean" err
+'
+
+test_expect_success TTY 'default: single match interactive, answer n exits cleanly' '
+	git config --unset help.autocorrect &&
+
+	write_script answer-prompt-no <<-\EOF &&
+		printf "n\n" >/dev/tty
+		exec "$@"
+	EOF
+
+	test_must_fail test_terminal ./answer-prompt-no git typotest 2>err &&
+	grep "Did you mean" err
+'
+
 test_done
-- 
2.50.1