run-command: expose is_executable function

Move the logic for 'is_executable()' from help.c to run_command.c and
expose it so that callers from outside help.c can access the function.
This is to enable run-command to be able to query if a file is
executable in a future patch.

Signed-off-by: Brandon Williams <bmwill@google.com>
Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

help.c

@@ -1,6 +1,7 @@
 #include "cache.h"
 #include "builtin.h"
 #include "exec_cmd.h"
+#include "run-command.h"
 #include "levenshtein.h"
 #include "help.h"
 #include "common-cmds.h"
@@ -96,48 +97,6 @@ static void pretty_print_cmdnames(struct cmdnames *cmds, unsigned int colopts)
 	string_list_clear(&list, 0);
 }
 
-static int is_executable(const char *name)
-{
-	struct stat st;
-
-	if (stat(name, &st) || /* stat, not lstat */
-	    !S_ISREG(st.st_mode))
-		return 0;
-
-#if defined(GIT_WINDOWS_NATIVE)
-	/*
-	 * On Windows there is no executable bit. The file extension
-	 * indicates whether it can be run as an executable, and Git
-	 * has special-handling to detect scripts and launch them
-	 * through the indicated script interpreter. We test for the
-	 * file extension first because virus scanners may make
-	 * it quite expensive to open many files.
-	 */
-	if (ends_with(name, ".exe"))
-		return S_IXUSR;
-
-{
-	/*
-	 * Now that we know it does not have an executable extension,
-	 * peek into the file instead.
-	 */
-	char buf[3] = { 0 };
-	int n;
-	int fd = open(name, O_RDONLY);
-	st.st_mode &= ~S_IXUSR;
-	if (fd >= 0) {
-		n = read(fd, buf, 2);
-		if (n == 2)
-			/* look for a she-bang */
-			if (!strcmp(buf, "#!"))
-				st.st_mode |= S_IXUSR;
-		close(fd);
-	}
-}
-#endif
-	return st.st_mode & S_IXUSR;
-}
-
 static void list_commands_in_dir(struct cmdnames *cmds,
 					 const char *path,
 					 const char *prefix)

run-command.c

@@ -117,6 +117,48 @@ static inline void close_pair(int fd[2])
 	close(fd[1]);
 }
 
+int is_executable(const char *name)
+{
+	struct stat st;
+
+	if (stat(name, &st) || /* stat, not lstat */
+	    !S_ISREG(st.st_mode))
+		return 0;
+
+#if defined(GIT_WINDOWS_NATIVE)
+	/*
+	 * On Windows there is no executable bit. The file extension
+	 * indicates whether it can be run as an executable, and Git
+	 * has special-handling to detect scripts and launch them
+	 * through the indicated script interpreter. We test for the
+	 * file extension first because virus scanners may make
+	 * it quite expensive to open many files.
+	 */
+	if (ends_with(name, ".exe"))
+		return S_IXUSR;
+
+{
+	/*
+	 * Now that we know it does not have an executable extension,
+	 * peek into the file instead.
+	 */
+	char buf[3] = { 0 };
+	int n;
+	int fd = open(name, O_RDONLY);
+	st.st_mode &= ~S_IXUSR;
+	if (fd >= 0) {
+		n = read(fd, buf, 2);
+		if (n == 2)
+			/* look for a she-bang */
+			if (!strcmp(buf, "#!"))
+				st.st_mode |= S_IXUSR;
+		close(fd);
+	}
+}
+#endif
+	return st.st_mode & S_IXUSR;
+}
+
 static char *locate_in_PATH(const char *file)
 {
 	const char *p = getenv("PATH");

run-command.h

@@ -51,6 +51,7 @@ struct child_process {
 #define CHILD_PROCESS_INIT { NULL, ARGV_ARRAY_INIT, ARGV_ARRAY_INIT }
 void child_process_init(struct child_process *);
 void child_process_clear(struct child_process *);
+extern int is_executable(const char *name);
 
 int start_command(struct child_process *);
 int finish_command(struct child_process *);