RFC [PATCH 1/3] files: when a filename with a colon and digits exists, open that file

When the user specifies, on the command line, a filename that ends with
a colon plus digits, and that filename exists in the file system, then
open that file, instead of interpreting the digits as a line number.

Also, if the filename stripped of the colon plus digits does not exist,
then do not interpret the digits as a line number either but treat them
as part of the file name.

Before this change, the user would have to escape the colon whenever
they wanted to open a file whose name ended with a colon plus digits.
Now the user needs to escape the colon only when 'foo' exists and they
want to create, say, 'foo:24'.

Problem-was-reported-by: Ralph Corderoy <[email protected]>
  https://lists.gnu.org/archive/html/nano-devel/2024-05/msg00001.html
Mitigation-was-suggested-by: Mike Scalora <[email protected]>
  https://lists.gnu.org/archive/html/nano-devel/2024-05/msg00008.html
---
 src/nano.c | 9 +++++++--
 1 file changed, 7 insertions(+), 2 deletions(-)

diff --git a/src/nano.c b/src/nano.c
index 973054f0..0467504f 100644
--- a/src/nano.c
+++ b/src/nano.c
@@ -2495,19 +2495,24 @@ int main(int argc, char **argv)
 		{
 			char *filename = argv[optind++];
 			char *colon = filename + (*filename ? 1 : 0);
+			struct stat fileinfo;
 
 			/* Search the filename for a colon.  If the colon is preceded by
 			 * a backslash, elide the backslash and skip the colon.  If there
 			 * is a valid number after the colon, chop colon and number off.
 			 * The number is later used to place the cursor on that line. */
+			if (strchr(filename, ':') && stat(filename, &fileinfo) < 0) {
 			while ((colon = strchr(colon, ':'))) {
 				if (*(colon - 1) == '\\')
 					memmove(colon - 1, colon, strlen(colon) + 1);
-				else if (parse_line_column(colon + 1, &givenline, &givencol))
+				else if (parse_line_column(colon + 1, &givenline, &givencol)) {
 					*colon = '\0';
-				else
+					if (stat(filename, &fileinfo) < 0)
+						*colon++ = ':';
+				} else
 					++colon;
 			}
+			}
 
 			if (!open_buffer(filename, TRUE))
 				continue;
-- 
2.42.1