config: really keep value-internal whitespace verbatim

Fix a bug in function parse_value() that prevented whitespace characters
(i.e. spaces and horizontal tabs) found inside configuration option values
from being parsed and returned in their original form.  The bug caused any
number of consecutive whitespace characters to be wrongly "squashed" into
the same number of space characters.

This bug was introduced back in July 2009, in commit ebdaae3 ("config:
Keep inner whitespace verbatim").

Further investigation showed that setting a configuration value, by invoking
git-config(1), converts value-internal horizontal tabs into "\t" escape
sequences, which the buggy value-parsing logic in function parse_value()
didn't "squash" into spaces.  That's why the test included in the ebdaae3
commit passed, which presumably made the bug remain undetected for this long.
On the other hand, value-internal literal horizontal tab characters, found in
a configuration file edited by hand, do get "squashed" by the value-parsing
logic, so the right choice was to fix this bug by making the value-internal
whitespace characters preserved verbatim.

Signed-off-by: Dragan Simic <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: Dragan Simic

config.c

@@ -819,7 +819,8 @@ static int get_next_char(struct config_source *cs)
 
 static char *parse_value(struct config_source *cs)
 {
-	int quote = 0, comment = 0, space = 0;
+	int quote = 0, comment = 0;
+	size_t trim_len = 0;
 
 	strbuf_reset(&cs->value);
 	for (;;) {
@@ -829,13 +830,17 @@ static char *parse_value(struct config_source *cs)
 				cs->linenr--;
 				return NULL;
 			}
+			if (trim_len)
+				strbuf_setlen(&cs->value, trim_len);
 			return cs->value.buf;
 		}
 		if (comment)
 			continue;
 		if (isspace(c) && !quote) {
+			if (!trim_len)
+				trim_len = cs->value.len;
 			if (cs->value.len)
-				space++;
+				strbuf_addch(&cs->value, c);
 			continue;
 		}
 		if (!quote) {
@@ -844,8 +849,8 @@ static char *parse_value(struct config_source *cs)
 				continue;
 			}
 		}
-		for (; space; space--)
-			strbuf_addch(&cs->value, ' ');
+		if (trim_len)
+			trim_len = 0;
 		if (c == '\\') {
 			c = get_next_char(cs);
 			switch (c) {