[PATCH v2 2/5] config: really keep value-internal whitespace verbatim

From: Dragan Simic <dsimic@manjaro.org>
Date: Mar 17, 2024, 03:48 UTC
Message-ID: <f4706cb73cd88139fda8bb09950d98d62f013e61.1710646998.git.dsimic@manjaro.org>
In-Reply-To: <cover.1710646998.git.dsimic@manjaro.org>

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 ebdaae372b46 ("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 ebdaae37 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 <dsimic@manjaro.org>
---

Notes:
    Changes in v2:
        - Dropped the "Fixes" tag, as explained and requested by Junio, [1]
          because having such tags actually doesn't help us in the long run
        - No changes to the source code were introduced
    
    [1] https://lore.kernel.org/git/xmqq4jd7qtg6.fsf@gitster.g/

 config.c | 13 +++++++++----
 1 file changed, 9 insertions(+), 4 deletions(-)

diff --git a/config.c b/config.c
index a86a20cdf5cb..5072f12e62e4 100644
--- a/config.c
+++ b/config.c
@@ -817,33 +817,38 @@ 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 (;;) {
 		int c = get_next_char(cs);
 		if (c == '\n') {
 			if (quote) {
 				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) {
 			if (c == ';' || c == '#') {
 				comment = 1;
 				continue;
 			}
 		}
-		for (; space; space--)
-			strbuf_addch(&cs->value, ' ');
+		if (trim_len)
+			trim_len = 0;
 		if (c == '\\') {
 			c = get_next_char(cs);
 			switch (c) {