diff --git a/base85.c b/base85.c
index b88270f9084409..24ddf60eb0a20f 100644
--- a/base85.c
+++ b/base85.c
@@ -57,14 +57,8 @@ int decode_85(char *dst, const char *buffer, int len)
 		de = de85[ch];
 		if (--de < 0)
 			return error("invalid base85 alphabet %c", ch);
-		/*
-		 * Detect overflow.  The largest
-		 * 5-letter possible is "|NsC0" to
-		 * encode 0xffffffff, and "|NsC" gives
-		 * 0x03030303 at this point (i.e.
-		 * 0xffffffff = 0x03030303 * 85).
-		 */
-		if (0x03030303 < acc ||
+		/* Detect overflow. */
+		if (0xffffffff / 85 < acc ||
 		    0xffffffff - de < (acc *= 85))
 			return error("invalid base85 sequence %.5s", buffer-5);
 		acc += de;
@@ -84,8 +78,6 @@ int decode_85(char *dst, const char *buffer, int len)
 
 void encode_85(char *buf, const unsigned char *data, int bytes)
 {
-	prep_base85();
-
 	say("encode 85");
 	while (bytes) {
 		unsigned acc = 0;
@@ -118,7 +110,7 @@ int main(int ac, char **av)
 		int len = strlen(av[2]);
 		encode_85(buf, av[2], len);
 		if (len <= 26) len = len + 'A' - 1;
-		else len = len + 'a' - 26 + 1;
+		else len = len + 'a' - 26 - 1;
 		printf("encoded: %c%s\n", len, buf);
 		return 0;
 	}
diff --git a/builtin-branch.c b/builtin-branch.c
index 23b6949fec30e8..7c615871100aa8 100644
--- a/builtin-branch.c
+++ b/builtin-branch.c
@@ -583,10 +583,12 @@ int cmd_branch(int argc, const char **argv, const char *prefix)
 		rename_branch(head, argv[0], rename > 1);
 	else if (rename && (argc == 2))
 		rename_branch(argv[0], argv[1], rename > 1);
-	else if (argc <= 2)
+	else if (argc <= 2) {
+		if (kinds != REF_LOCAL_BRANCH)
+			die("-a and -r options to 'git branch' do not make sense with a branch name");
 		create_branch(head, argv[0], (argc == 2) ? argv[1] : head,
 			      force_create, reflog, track);
-	else
+	} else
 		usage_with_options(builtin_branch_usage, options);
 
 	return 0;
diff --git a/builtin-checkout.c b/builtin-checkout.c
index b5dd9c07b42e01..f32b14838d7189 100644
--- a/builtin-checkout.c
+++ b/builtin-checkout.c
@@ -403,7 +403,7 @@ static int merge_working_tree(struct checkout_opts *opts,
 		topts.initial_checkout = is_cache_unborn();
 		topts.update = 1;
 		topts.merge = 1;
-		topts.gently = opts->merge;
+		topts.gently = opts->merge && old->commit;
 		topts.verbose_update = !opts->quiet;
 		topts.fn = twoway_merge;
 		topts.dir = xcalloc(1, sizeof(*topts.dir));
@@ -426,7 +426,13 @@ static int merge_working_tree(struct checkout_opts *opts,
 			struct merge_options o;
 			if (!opts->merge)
 				return 1;
-			parse_commit(old->commit);
+
+			/*
+			 * Without old->commit, the below is the same as
+			 * the two-tree unpack we already tried and failed.
+			 */
+			if (!old->commit)
+				return 1;
 
 			/* Do more real merge */
 
diff --git a/t/t5403-post-checkout-hook.sh b/t/t5403-post-checkout-hook.sh
index 9b2e1a94c5fb5a..a7bef9371fc190 100755
--- a/t/t5403-post-checkout-hook.sh
+++ b/t/t5403-post-checkout-hook.sh
@@ -7,19 +7,19 @@ test_description='Test the post-checkout hook.'
 . ./test-lib.sh
 
 test_expect_success setup '
-	 echo Data for commit0. >a &&
-	 echo Data for commit0. >b &&
-	 git update-index --add a &&
-	 git update-index --add b &&
-	 tree0=$(git write-tree) &&
-	 commit0=$(echo setup | git commit-tree $tree0) &&
-        git update-ref refs/heads/master $commit0 &&
-	 git clone ./. clone1 &&
-	 git clone ./. clone2 &&
-        GIT_DIR=clone2/.git git branch -a new2 &&
-        echo Data for commit1. >clone2/b &&
-	 GIT_DIR=clone2/.git git add clone2/b &&
-	 GIT_DIR=clone2/.git git commit -m new2
+	echo Data for commit0. >a &&
+	echo Data for commit0. >b &&
+	git update-index --add a &&
+	git update-index --add b &&
+	tree0=$(git write-tree) &&
+	commit0=$(echo setup | git commit-tree $tree0) &&
+	git update-ref refs/heads/master $commit0 &&
+	git clone ./. clone1 &&
+	git clone ./. clone2 &&
+	GIT_DIR=clone2/.git git branch new2 &&
+	echo Data for commit1. >clone2/b &&
+	GIT_DIR=clone2/.git git add clone2/b &&
+	GIT_DIR=clone2/.git git commit -m new2
 '
 
 for clone in 1 2; do