help.c: help.autocorrect=prompt waits for user action

If help.autocorrect is set to 'prompt', the user is prompted
before the suggested action is executed.

Based on original patch by David Barr
https://lore.kernel.org/git/1283758030-13345-1-git-send-email-david.barr@cordelta.com/

Signed-off-by: Azeem Bande-Ali <me@azeemba.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/config/help.txt

@@ -9,13 +9,15 @@ help.format::
 
 help.autoCorrect::
 	If git detects typos and can identify exactly one valid command similar
-	to the error, git will automatically run the intended command after
-	waiting a duration of time defined by this configuration value in
-	deciseconds (0.1 sec).  If this value is 0, the suggested corrections
-	will be shown, but not executed. If it is a negative integer, or
-	"immediate", the suggested command
-	is run immediately. If "never", suggestions are not shown at all. The
-	default value is zero.
+	to the error, git will try to suggest the correct command or even
+	run the suggestion automatically. Possible config values are:
+	 - 0 (default): show the suggested command.
+	 - positive number: run the suggested command after specified
+deciseconds (0.1 sec).
+	 - "immediate": run the suggested command immediately.
+	 - "prompt": show the suggestion and prompt for confirmation to run
+the command.
+	 - "never": don't run or show any suggested command.
 
 help.htmlPath::
 	Specify the path where the HTML documentation resides. File system paths

help.c

@@ -11,6 +11,7 @@
 #include "version.h"
 #include "refs.h"
 #include "parse-options.h"
+#include "prompt.h"
 
 struct category_description {
 	uint32_t category;
@@ -472,6 +473,7 @@ int is_in_cmdlist(struct cmdnames *c, const char *s)
 static int autocorrect;
 static struct cmdnames aliases;
 
+#define AUTOCORRECT_PROMPT (-3)
 #define AUTOCORRECT_NEVER (-2)
 #define AUTOCORRECT_IMMEDIATELY (-1)
 
@@ -486,6 +488,8 @@ static int git_unknown_cmd_config(const char *var, const char *value, void *cb)
 			autocorrect = AUTOCORRECT_NEVER;
 		} else if (!strcmp(value, "immediate")) {
 			autocorrect = AUTOCORRECT_IMMEDIATELY;
+		} else if (!strcmp(value, "prompt")) {
+			autocorrect = AUTOCORRECT_PROMPT;
 		} else {
 			int v = git_config_int(var, value);
 			autocorrect = (v < 0)
@@ -539,6 +543,12 @@ const char *help_unknown_cmd(const char *cmd)
 
 	read_early_config(git_unknown_cmd_config, NULL);
 
+	/*
+	 * Disable autocorrection prompt in a non-interactive session
+	 */
+	if ((autocorrect == AUTOCORRECT_PROMPT) && (!isatty(0) || !isatty(2)))
+		autocorrect = AUTOCORRECT_NEVER;
+
 	if (autocorrect == AUTOCORRECT_NEVER) {
 		fprintf_ln(stderr, _("git: '%s' is not a git command. See 'git --help'."), cmd);
 		exit(1);
@@ -618,7 +628,16 @@ const char *help_unknown_cmd(const char *cmd)
 				   _("Continuing under the assumption that "
 				     "you meant '%s'."),
 				   assumed);
-		else {
+		else if (autocorrect == AUTOCORRECT_PROMPT) {
+			char *answer;
+			struct strbuf msg = STRBUF_INIT;
+			strbuf_addf(&msg, _("Run '%s' instead? (y/N)"), assumed);
+			answer = git_prompt(msg.buf, PROMPT_ECHO);
+			strbuf_release(&msg);
+			if (!(starts_with(answer, "y") ||
+			      starts_with(answer, "Y")))
+				exit(1);
+		} else {
 			fprintf_ln(stderr,
 				   _("Continuing in %0.1f seconds, "
 				     "assuming that you meant '%s'."),