interactive: refactor code asking the user for interactive input

There are quite a few code locations (e.g. `git clean --interactive`)
where Git asks the user for an answer. In preparation for fixing a bug
shared by all of them, and also to DRY up the code, let's refactor it.

Please note that most of these callers trimmed white-space both at the
beginning and at the end of the answer, instead of trimming only the
end (as the caller in `add-patch.c` does).

Therefore, technically speaking, we change behavior in this patch. At
the same time, it can be argued that this is actually a bug fix.

Signed-off-by: Johannes Schindelin <johannes.schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

add-interactive.c

@@ -9,6 +9,7 @@
 #include "lockfile.h"
 #include "dir.h"
 #include "run-command.h"
+#include "prompt.h"
 
 static void init_color(struct repository *r, struct add_i_state *s,
 		       const char *slot_name, char *dst,
@@ -289,13 +290,12 @@ static ssize_t list_and_choose(struct add_i_state *s,
 		fputs(singleton ? "> " : ">> ", stdout);
 		fflush(stdout);
 
-		if (strbuf_getline(&input, stdin) == EOF) {
+		if (git_read_line_interactively(&input) == EOF) {
 			putchar('\n');
 			if (immediate)
 				res = LIST_AND_CHOOSE_QUIT;
 			break;
 		}
-		strbuf_trim(&input);
 
 		if (!input.len)
 			break;

add-patch.c

@@ -7,6 +7,7 @@
 #include "color.h"
 #include "diff.h"
 #include "compat/terminal.h"
+#include "prompt.h"
 
 enum prompt_mode_type {
 	PROMPT_MODE_CHANGE = 0, PROMPT_DELETION, PROMPT_HUNK,
@@ -1158,9 +1159,8 @@ static int read_single_character(struct add_p_state *s)
 		return res;
 	}
 
-	if (strbuf_getline(&s->answer, stdin) == EOF)
+	if (git_read_line_interactively(&s->answer) == EOF)
 		return EOF;
-	strbuf_trim_trailing_newline(&s->answer);
 	return 0;
 }
 

builtin/clean.c

@@ -18,6 +18,7 @@
 #include "color.h"
 #include "pathspec.h"
 #include "help.h"
+#include "prompt.h"
 
 static int force = -1; /* unset */
 static int interactive;
@@ -420,7 +421,6 @@ static int find_unique(const char *choice, struct menu_stuff *menu_stuff)
 	return found;
 }
 
-
 /*
  * Parse user input, and return choice(s) for menu (menu_stuff).
  *
@@ -580,9 +580,7 @@ static int *list_and_choose(struct menu_opts *opts, struct menu_stuff *stuff)
 			       clean_get_color(CLEAN_COLOR_RESET));
 		}
 
-		if (strbuf_getline_lf(&choice, stdin) != EOF) {
-			strbuf_trim(&choice);
-		} else {
+		if (git_read_line_interactively(&choice) == EOF) {
 			eof = 1;
 			break;
 		}
@@ -662,9 +660,7 @@ static int filter_by_patterns_cmd(void)
 		clean_print_color(CLEAN_COLOR_PROMPT);
 		printf(_("Input ignore patterns>> "));
 		clean_print_color(CLEAN_COLOR_RESET);
-		if (strbuf_getline_lf(&confirm, stdin) != EOF)
-			strbuf_trim(&confirm);
-		else
+		if (git_read_line_interactively(&confirm) == EOF)
 			putchar('\n');
 
 		/* quit filter_by_pattern mode if press ENTER or Ctrl-D */
@@ -760,9 +756,7 @@ static int ask_each_cmd(void)
 			qname = quote_path_relative(item->string, NULL, &buf);
 			/* TRANSLATORS: Make sure to keep [y/N] as is */
 			printf(_("Remove %s [y/N]? "), qname);
-			if (strbuf_getline_lf(&confirm, stdin) != EOF) {
-				strbuf_trim(&confirm);
-			} else {
+			if (git_read_line_interactively(&confirm) == EOF) {
 				putchar('\n');
 				eof = 1;
 			}

prompt.c

@@ -74,3 +74,13 @@ char *git_prompt(const char *prompt, int flags)
 	}
 	return r;
 }
+
+int git_read_line_interactively(struct strbuf *line)
+{
+	int ret = strbuf_getline_lf(line, stdin);
+
+	if (ret != EOF)
+		strbuf_trim_trailing_newline(line);
+
+	return ret;
+}

prompt.h

@@ -6,4 +6,6 @@
 
 char *git_prompt(const char *prompt, int flags);
 
+int git_read_line_interactively(struct strbuf *line);
+
 #endif /* PROMPT_H */

shell.c

@@ -4,6 +4,7 @@
 #include "strbuf.h"
 #include "run-command.h"
 #include "alias.h"
+#include "prompt.h"
 
 #define COMMAND_DIR "git-shell-commands"
 #define HELP_COMMAND COMMAND_DIR "/help"
@@ -76,12 +77,11 @@ static void run_shell(void)
 		int count;
 
 		fprintf(stderr, "git> ");
-		if (strbuf_getline_lf(&line, stdin) == EOF) {
+		if (git_read_line_interactively(&line) == EOF) {
 			fprintf(stderr, "\n");
 			strbuf_release(&line);
 			break;
 		}
-		strbuf_trim(&line);
 		rawargs = strbuf_detach(&line, NULL);
 		split_args = xstrdup(rawargs);
 		count = split_cmdline(split_args, &argv);