Merge branch 'jk/connect-clear-env' into maint

The ssh transport, just like any other transport over the network,
did not clear GIT_* environment variables, but it is possible to
use SendEnv and AcceptEnv to leak them to the remote invocation of
Git, which is not a good idea at all.  Explicitly clear them just
like we do for the local transport.

* jk/connect-clear-env:
  git_connect: clarify conn->use_shell flag
  git_connect: clear GIT_* environment for ssh

connect.c

@@ -724,10 +724,13 @@ struct child_process *git_connect(int fd[2], const char *url,
 		strbuf_addch(&cmd, ' ');
 		sq_quote_buf(&cmd, path);
 
+		/* remove repo-local variables from the environment */
+		conn->env = local_repo_env;
+		conn->use_shell = 1;
 		conn->in = conn->out = -1;
 		if (protocol == PROTO_SSH) {
 			const char *ssh;
-			int putty, tortoiseplink = 0;
+			int putty = 0, tortoiseplink = 0;
 			char *ssh_host = hostandport;
 			const char *port = NULL;
 			transport_check_allowed("ssh");
@@ -750,13 +753,17 @@ struct child_process *git_connect(int fd[2], const char *url,
 			}
 
 			ssh = getenv("GIT_SSH_COMMAND");
-			if (ssh) {
-				conn->use_shell = 1;
-				putty = 0;
-			} else {
+			if (!ssh) {
 				const char *base;
 				char *ssh_dup;
 
+				/*
+				 * GIT_SSH is the no-shell version of
+				 * GIT_SSH_COMMAND (and must remain so for
+				 * historical compatibility).
+				 */
+				conn->use_shell = 0;
+
 				ssh = getenv("GIT_SSH");
 				if (!ssh)
 					ssh = "ssh";
@@ -766,8 +773,9 @@ struct child_process *git_connect(int fd[2], const char *url,
 
 				tortoiseplink = !strcasecmp(base, "tortoiseplink") ||
 					!strcasecmp(base, "tortoiseplink.exe");
-				putty = !strcasecmp(base, "plink") ||
-					!strcasecmp(base, "plink.exe") || tortoiseplink;
+				putty = tortoiseplink ||
+					!strcasecmp(base, "plink") ||
+					!strcasecmp(base, "plink.exe");
 
 				free(ssh_dup);
 			}
@@ -782,9 +790,6 @@ struct child_process *git_connect(int fd[2], const char *url,
 			}
 			argv_array_push(&conn->args, ssh_host);
 		} else {
-			/* remove repo-local variables from the environment */
-			conn->env = local_repo_env;
-			conn->use_shell = 1;
 			transport_check_allowed("file");
 		}
 		argv_array_push(&conn->args, cmd.buf);

t/t5507-remote-environment.sh

@@ -0,0 +1,34 @@
+#!/bin/sh
+
+test_description='check environment showed to remote side of transports'
+. ./test-lib.sh
+
+test_expect_success 'set up "remote" push situation' '
+	test_commit one &&
+	git config push.default current &&
+	git init remote
+'
+
+test_expect_success 'set up fake ssh' '
+	GIT_SSH_COMMAND="f() {
+		cd \"\$TRASH_DIRECTORY\" &&
+		eval \"\$2\"
+	}; f" &&
+	export GIT_SSH_COMMAND &&
+	export TRASH_DIRECTORY
+'
+
+# due to receive.denyCurrentBranch=true
+test_expect_success 'confirm default push fails' '
+	test_must_fail git push remote
+'
+
+test_expect_success 'config does not travel over same-machine push' '
+	test_must_fail git -c receive.denyCurrentBranch=false push remote
+'
+
+test_expect_success 'config does not travel over ssh push' '
+	test_must_fail git -c receive.denyCurrentBranch=false push host:remote
+'
+
+test_done