git_connect(): factor out SSH variant handling

We handle plink and tortoiseplink as OpenSSH replacements, by passing
the correct command-line options when detecting that they are used.

To let users override that auto-detection (in case Git gets it wrong),
we need to introduce new code to that end.

In preparation for this code, let's factor out the SSH variant handling
into its own function, handle_ssh_variant().

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

connect.c

@@ -691,6 +691,44 @@ static const char *get_ssh_command(void)
 	return NULL;
 }
 
+static int handle_ssh_variant(const char *ssh_command, int is_cmdline,
+			      int *port_option, int *needs_batch)
+{
+	const char *variant;
+	char *p = NULL;
+
+	if (!is_cmdline) {
+		p = xstrdup(ssh_command);
+		variant = basename(p);
+	} else {
+		const char **ssh_argv;
+
+		p = xstrdup(ssh_command);
+		if (split_cmdline(p, &ssh_argv)) {
+			variant = basename((char *)ssh_argv[0]);
+			/*
+			 * At this point, variant points into the buffer
+			 * referenced by p, hence we do not need ssh_argv
+			 * any longer.
+			 */
+			free(ssh_argv);
+		} else
+			return 0;
+	}
+
+	if (!strcasecmp(variant, "plink") ||
+	    !strcasecmp(variant, "plink.exe"))
+		*port_option = 'P';
+	else if (!strcasecmp(variant, "tortoiseplink") ||
+		 !strcasecmp(variant, "tortoiseplink.exe")) {
+		*port_option = 'P';
+		*needs_batch = 1;
+	}
+	free(p);
+
+	return 1;
+}
+
 /*
  * This returns a dummy child_process if the transport protocol does not
  * need fork(2), or a struct child_process object if it does.  Once done,
@@ -773,7 +811,6 @@ struct child_process *git_connect(int fd[2], const char *url,
 			int port_option = 'p';
 			char *ssh_host = hostandport;
 			const char *port = NULL;
-			char *ssh_argv0 = NULL;
 			transport_check_allowed("ssh");
 			get_host_and_port(&ssh_host, &port);
 
@@ -794,15 +831,10 @@ struct child_process *git_connect(int fd[2], const char *url,
 			}
 
 			ssh = get_ssh_command();
-			if (ssh) {
-				char *split_ssh = xstrdup(ssh);
-				const char **ssh_argv;
-
-				if (split_cmdline(split_ssh, &ssh_argv))
-					ssh_argv0 = xstrdup(ssh_argv[0]);
-				free(split_ssh);
-				free((void *)ssh_argv);
-			} else {
+			if (ssh)
+				handle_ssh_variant(ssh, 1, &port_option,
+						   &needs_batch);
+			else {
 				/*
 				 * GIT_SSH is the no-shell version of
 				 * GIT_SSH_COMMAND (and must remain so for
@@ -813,22 +845,10 @@ struct child_process *git_connect(int fd[2], const char *url,
 				ssh = getenv("GIT_SSH");
 				if (!ssh)
 					ssh = "ssh";
-
-				ssh_argv0 = xstrdup(ssh);
-			}
-
-			if (ssh_argv0) {
-				const char *base = basename(ssh_argv0);
-
-				if (!strcasecmp(base, "tortoiseplink") ||
-				    !strcasecmp(base, "tortoiseplink.exe")) {
-					port_option = 'P';
-					needs_batch = 1;
-				} else if (!strcasecmp(base, "plink") ||
-					   !strcasecmp(base, "plink.exe")) {
-					port_option = 'P';
-				}
-				free(ssh_argv0);
+				else
+					handle_ssh_variant(ssh, 0,
+							   &port_option,
+							   &needs_batch);
 			}
 
 			argv_array_push(&conn->args, ssh);