config: handle lack of newline at end of file better

The config parsing routines use the static global
'config_file' to store the FILE* pointing to the current
config file being parsed. The function get_next_char()
automatically converts an EOF on this file to a newline for
the convenience of its callers, and it sets config_file to
NULL to indicate that EOF was reached.

This throws away useful information, though, since some
routines want to call ftell on 'config_file' to find out
exactly _where_ the routine ended. In the case of a key
ending at EOF boundary, we ended up segfaulting in some
cases (changing that key or adding another key in its
section), or failing to provide the necessary newline
(adding a new section).

This patch adds a new flag to indicate EOF and uses that
instead of setting config_file to NULL. It also makes sure
to add newlines where necessary for truncated input. All
three included tests fail without the patch.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

config.c

@@ -13,6 +13,7 @@
 static FILE *config_file;
 static const char *config_file_name;
 static int config_linenr;
+static int config_file_eof;
 static int zlib_compression_seen;
 
 static int get_next_char(void)
@@ -34,7 +35,7 @@ static int get_next_char(void)
 		if (c == '\n')
 			config_linenr++;
 		if (c == EOF) {
-			config_file = NULL;
+			config_file_eof = 1;
 			c = '\n';
 		}
 	}
@@ -118,7 +119,7 @@ static int get_value(config_fn_t fn, char *name, unsigned int len)
 	/* Get the full name */
 	for (;;) {
 		c = get_next_char();
-		if (c == EOF)
+		if (config_file_eof)
 			break;
 		if (!iskeychar(c))
 			break;
@@ -182,7 +183,7 @@ static int get_base_var(char *name)
 
 	for (;;) {
 		int c = get_next_char();
-		if (c == EOF)
+		if (config_file_eof)
 			return -1;
 		if (c == ']')
 			return baselen;
@@ -205,8 +206,7 @@ static int git_parse_file(config_fn_t fn)
 	for (;;) {
 		int c = get_next_char();
 		if (c == '\n') {
-			/* EOF? */
-			if (!config_file)
+			if (config_file_eof)
 				return 0;
 			comment = 0;
 			continue;
@@ -469,6 +469,7 @@ int git_config_from_file(config_fn_t fn, const char *filename)
 		config_file = f;
 		config_file_name = filename;
 		config_linenr = 1;
+		config_file_eof = 0;
 		ret = git_parse_file(fn);
 		fclose(f);
 		config_file_name = NULL;
@@ -918,6 +919,9 @@ int git_config_set_multivar(const char* key, const char* value,
 					contents, contents_sz,
 					store.offset[i]-2, &new_line);
 
+			if (copy_end > 0 && contents[copy_end-1] != '\n')
+				new_line = 1;
+
 			/* write the first part of the config */
 			if (copy_end > copy_begin) {
 				if (write_in_full(fd, contents + copy_begin,

t/t1303-wacky-config.sh

@@ -0,0 +1,37 @@
+#!/bin/sh
+
+test_description='Test wacky input to git config'
+. ./test-lib.sh
+
+setup() {
+	(printf "[section]\n" &&
+	printf "  key = foo") >.git/config
+}
+
+check() {
+	echo "$2" >expected
+	git config --get "$1" >actual
+	git diff actual expected
+}
+
+test_expect_success 'modify same key' '
+	setup &&
+	git config section.key bar &&
+	check section.key bar
+'
+
+test_expect_success 'add key in same section' '
+	setup &&
+	git config section.other bar &&
+	check section.key foo &&
+	check section.other bar
+'
+
+test_expect_success 'add key in different section' '
+	setup &&
+	git config section2.key bar &&
+	check section.key foo &&
+	check section2.key bar
+'
+
+test_done