Merge branch 'js/run-command-updates'

* js/run-command-updates:
  api-run-command.txt: describe error behavior of run_command functions
  run-command.c: squelch a "use before assignment" warning
  receive-pack: remove unnecessary run_status report
  run_command: report failure to execute the program, but optionally don't
  run_command: encode deadly signal number in the return value
  run_command: report system call errors instead of returning error codes
  run_command: return exit code as positive value
  MinGW: simplify waitpid() emulation macros

Documentation/technical/api-run-command.txt

@@ -35,12 +35,32 @@ Functions
 	Convenience functions that encapsulate a sequence of
 	start_command() followed by finish_command(). The argument argv
 	specifies the program and its arguments. The argument opt is zero
-	or more of the flags `RUN_COMMAND_NO_STDIN`, `RUN_GIT_CMD`, or
-	`RUN_COMMAND_STDOUT_TO_STDERR` that correspond to the members
-	.no_stdin, .git_cmd, .stdout_to_stderr of `struct child_process`.
+	or more of the flags `RUN_COMMAND_NO_STDIN`, `RUN_GIT_CMD`,
+	`RUN_COMMAND_STDOUT_TO_STDERR`, or `RUN_SILENT_EXEC_FAILURE`
+	that correspond to the members .no_stdin, .git_cmd,
+	.stdout_to_stderr, .silent_exec_failure of `struct child_process`.
 	The argument dir corresponds the member .dir. The argument env
 	corresponds to the member .env.
 
+The functions above do the following:
+
+. If a system call failed, errno is set and -1 is returned. A diagnostic
+  is printed.
+
+. If the program was not found, then -1 is returned and errno is set to
+  ENOENT; a diagnostic is printed only if .silent_exec_failure is 0.
+
+. Otherwise, the program is run. If it terminates regularly, its exit
+  code is returned. No diagnistic is printed, even if the exit code is
+  non-zero.
+
+. If the program terminated due to a signal, then the return value is the
+  signal number - 128, ie. it is negative and so indicates an unusual
+  condition; a diagnostic is printed. This return value can be passed to
+  exit(2), which will report the same code to the parent process that a
+  POSIX shell's $? would report for a program that died from the signal.
+
+
 `start_async`::
 
 	Run a function asynchronously. Takes a pointer to a `struct
@@ -143,6 +163,11 @@ string pointers (NULL terminated) in .env:
 To specify a new initial working directory for the sub-process,
 specify it in the .dir member.
 
+If the program cannot be found, the functions return -1 and set
+errno to ENOENT. Normally, an error message is printed, but if
+.silent_exec_failure is set to 1, no message is printed for this
+special error condition.
+
 
 * `struct async`
 

builtin-merge.c

@@ -594,7 +594,7 @@ static int try_merge_strategy(const char *strategy, struct commit_list *common,
 		discard_cache();
 		if (read_cache() < 0)
 			die("failed to read the cache");
-		return -ret;
+		return ret;
 	}
 }
 

builtin-receive-pack.c

@@ -123,31 +123,6 @@ static struct command *commands;
 static const char pre_receive_hook[] = "hooks/pre-receive";
 static const char post_receive_hook[] = "hooks/post-receive";
 
-static int run_status(int code, const char *cmd_name)
-{
-	switch (code) {
-	case 0:
-		return 0;
-	case -ERR_RUN_COMMAND_FORK:
-		return error("fork of %s failed", cmd_name);
-	case -ERR_RUN_COMMAND_EXEC:
-		return error("execute of %s failed", cmd_name);
-	case -ERR_RUN_COMMAND_PIPE:
-		return error("pipe failed");
-	case -ERR_RUN_COMMAND_WAITPID:
-		return error("waitpid failed");
-	case -ERR_RUN_COMMAND_WAITPID_WRONG_PID:
-		return error("waitpid is confused");
-	case -ERR_RUN_COMMAND_WAITPID_SIGNAL:
-		return error("%s died of signal", cmd_name);
-	case -ERR_RUN_COMMAND_WAITPID_NOEXIT:
-		return error("%s died strangely", cmd_name);
-	default:
-		error("%s exited with error code %d", cmd_name, -code);
-		return -code;
-	}
-}
-
 static int run_receive_hook(const char *hook_name)
 {
 	static char buf[sizeof(commands->old_sha1) * 2 + PATH_MAX + 4];
@@ -174,7 +149,7 @@ static int run_receive_hook(const char *hook_name)
 
 	code = start_command(&proc);
 	if (code)
-		return run_status(code, hook_name);
+		return code;
 	for (cmd = commands; cmd; cmd = cmd->next) {
 		if (!cmd->error_string) {
 			size_t n = snprintf(buf, sizeof(buf), "%s %s %s\n",
@@ -186,7 +161,7 @@ static int run_receive_hook(const char *hook_name)
 		}
 	}
 	close(proc.in);
-	return run_status(finish_command(&proc), hook_name);
+	return finish_command(&proc);
 }
 
 static int run_update_hook(struct command *cmd)
@@ -203,9 +178,8 @@ static int run_update_hook(struct command *cmd)
 	argv[3] = sha1_to_hex(cmd->new_sha1);
 	argv[4] = NULL;
 
-	return run_status(run_command_v_opt(argv, RUN_COMMAND_NO_STDIN |
-					RUN_COMMAND_STDOUT_TO_STDERR),
-			update_hook);
+	return run_command_v_opt(argv, RUN_COMMAND_NO_STDIN |
+					RUN_COMMAND_STDOUT_TO_STDERR);
 }
 
 static int is_ref_checked_out(const char *ref)
@@ -419,7 +393,6 @@ static void run_update_post_hook(struct command *cmd)
 	argv[argc] = NULL;
 	status = run_command_v_opt(argv, RUN_COMMAND_NO_STDIN
 			| RUN_COMMAND_STDOUT_TO_STDERR);
-	run_status(status, update_post_hook);
 }
 
 static void execute_commands(const char *unpacker_error)
@@ -537,7 +510,6 @@ static const char *unpack(void)
 		code = run_command_v_opt(unpacker, RUN_GIT_CMD);
 		if (!code)
 			return NULL;
-		run_status(code, unpacker[0]);
 		return "unpack-objects abnormal exit";
 	} else {
 		const char *keeper[7];
@@ -563,7 +535,6 @@ static const char *unpack(void)
 		ip.git_cmd = 1;
 		status = start_command(&ip);
 		if (status) {
-			run_status(status, keeper[0]);
 			return "index-pack fork failed";
 		}
 		pack_lockfile = index_pack_lockfile(ip.out);
@@ -573,7 +544,6 @@ static const char *unpack(void)
 			reprepare_packed_git();
 			return NULL;
 		}
-		run_status(status, keeper[0]);
 		return "index-pack abnormal exit";
 	}
 }

compat/mingw.h

@@ -17,9 +17,10 @@ typedef int pid_t;
 #define S_IROTH 0
 #define S_IXOTH 0
 
-#define WIFEXITED(x) ((unsigned)(x) < 259)	/* STILL_ACTIVE */
+#define WIFEXITED(x) 1
+#define WIFSIGNALED(x) 0
 #define WEXITSTATUS(x) ((x) & 0xff)
-#define WIFSIGNALED(x) ((unsigned)(x) > 259)
+#define WTERMSIG(x) SIGTERM
 
 #define SIGHUP 1
 #define SIGQUIT 3

convert.c

@@ -267,7 +267,7 @@ static int filter_buffer(int fd, void *data)
 
 	status = finish_command(&child_process);
 	if (status)
-		error("external filter %s failed %d", params->cmd, -status);
+		error("external filter %s failed %d", params->cmd, status);
 	return (write_err || status);
 }
 

git.c

@@ -416,13 +416,9 @@ static void execv_dashed_external(const char **argv)
 	 * if we fail because the command is not found, it is
 	 * OK to return. Otherwise, we just pass along the status code.
 	 */
-	status = run_command_v_opt(argv, 0);
-	if (status != -ERR_RUN_COMMAND_EXEC) {
-		if (IS_RUN_COMMAND_ERR(status))
-			die("unable to run '%s'", argv[0]);
-		exit(-status);
-	}
-	errno = ENOENT; /* as if we called execvp */
+	status = run_command_v_opt(argv, RUN_SILENT_EXEC_FAILURE);
+	if (status >= 0 || errno != ENOENT)
+		exit(status);
 
 	argv[0] = tmp;
 

ll-merge.c

@@ -192,10 +192,6 @@ static int ll_ext_merge(const struct ll_merge_driver *fn,
 
 	args[2] = cmd.buf;
 	status = run_command_v_opt(args, 0);
-	if (status < -ERR_RUN_COMMAND_FORK)
-		; /* failure in run-command */
-	else
-		status = -status;
 	fd = open(temp[1], O_RDONLY);
 	if (fd < 0)
 		goto bad;