vis: cleanup vis_pipe API

register.c

@@ -47,7 +47,7 @@ const char *register_get(Vis *vis, Register *reg, size_t *len) {
 
 		int status = vis_pipe(vis, &clipboard,
 			&(Filerange){ .start = 0, .end = 0 },
-			(const char*[]){ "vis-clipboard", "vis-clipboard", "--paste", NULL },
+			(const char*[]){ "vis-clipboard", "--paste", NULL },
 			read_stdout, read_stderr);
 		if (status != 0)
 			vis_info_show(vis, "Command failed %s", stderr.len > 0 ? stderr.data : "");
@@ -90,7 +90,7 @@ bool register_put_range(Vis *vis, Register *reg, Text *txt, Filerange *range) {
 		};
 
 		int status = vis_pipe(vis, &clipboard, range,
-			(const char*[]){ "vis-clipboard", "vis-clipboard", "--copy", NULL },
+			(const char*[]){ "vis-clipboard", "--copy", NULL },
 			NULL, read_stderr);
 
 		if (status != 0)

vis-cmds.c

@@ -700,10 +700,10 @@ int vis_pipe(Vis *vis, void *context, Filerange *range, const char *argv[],
 			dup2(perr[1], STDERR_FILENO);
 		close(perr[0]);
 		close(perr[1]);
-		if (!argv[2])
-			execl("/bin/sh", "sh", "-c", argv[1], NULL);
+		if (!argv[1])
+			execl("/bin/sh", "sh", "-c", argv[0], NULL);
 		else
-			execvp(argv[1], (char**)argv+1);
+			execvp(argv[0], (char* const*)argv);
 		vis_info_show(vis, "exec failure: %s", strerror(errno));
 		exit(EXIT_FAILURE);
 	}
@@ -848,7 +848,7 @@ static bool cmd_filter(Vis *vis, Filerange *range, enum CmdOpt opt, const char *
 
 	text_snapshot(txt);
 
-	int status = vis_pipe(vis, &filter, range, argv, read_stdout, read_stderr);
+	int status = vis_pipe(vis, &filter, range, &argv[1], read_stdout, read_stderr);
 
 	if (status == 0) {
 		if (text_range_valid(range)) {
@@ -902,7 +902,7 @@ static bool cmd_pipe(Vis *vis, Filerange *range, enum CmdOpt opt, const char *ar
 
 	buffer_init(&filter.err);
 
-	int status = vis_pipe(vis, &filter, range, argv, read_stdout_new, read_stderr);
+	int status = vis_pipe(vis, &filter, range, &argv[1], read_stdout_new, read_stderr);
 
 	if (vis->cancel_filter)
 		vis_info_show(vis, "Command cancelled");

vis.h

@@ -389,7 +389,16 @@ bool vis_cmd(Vis*, const char *cmd);
 /* execute any kind (:,?,/) of prompt command */
 bool vis_prompt_cmd(Vis*, const char *cmd);
 
-/* pipe a given file range to an external process */
+/* pipe a given file range to an external process
+ *
+ * if argv contains only one non-NULL element the command is executed using
+ * /bin/sh -c (i.e. argument expansion is performed by the shell). In contrast
+ * if argv contains more than one non-NULL element execvp(argv[0], argv); will
+ * be used.
+ *
+ * if read_std{out,err} are non-NULL they will be called when output from
+ * the forked process is available.
+ */
 int vis_pipe(Vis *vis, void *context, Filerange *range, const char *argv[],
 	ssize_t (*read_stdout)(void *context, char *data, size_t len),
 	ssize_t (*read_stderr)(void *context, char *data, size_t len));