[PATCH 1/2] files: look for digits and colons starting from the end of the filename

[Benno Schulenberg]

Starting from the end of the provided filename avoids needlessly looking
at colons that are somewhere in the middle of the path or the filename.

It also avoids inconsistenly interpreting a specified line number as a
column number when the filename itself ends with a colon plus digits
and the filename without the colon plus digits exists too.

This also removes the eliding of a backslash before a colon, which
would mangle the filename if the name actually contained a backslash
followed by a colon.

Negative line and column numbers are no longer allowed when using the
colon notation.

This fixes https://savannah.gnu.org/bugs/?65781,
and fixes https://savannah.gnu.org/bugs/?65782.

Problems existed since version 8.0, since colon parsing was introduced.
---
 src/nano.c | 32 ++++++++++++++++----------------
 1 file changed, 16 insertions(+), 16 deletions(-)

diff --git a/src/nano.c b/src/nano.c
index 123af18d..5707bd96 100644
--- a/src/nano.c
+++ b/src/nano.c
@@ -2500,24 +2500,24 @@ int main(int argc, char **argv)
                        struct stat fileinfo;
 
                        /* If the filename contains a colon and this file does 
not exist,
-                        * then check if the filename ends with a number (while 
skipping
-                        * any colon preceded by a backslash and eliding the 
backslash).
-                        * If there is a valid trailing number, chop colon and 
number off.
+                        * then check if the filename ends with digits preceded 
by a colon
+                        * (possibly preceded by more digits and a colon).  If 
there is or
+                        * are such trailing numbers, chop the colons plus 
numbers off.
                         * The number is later used to place the cursor on that 
line. */
                        if (strchr(filename, ':') && stat(filename, &fileinfo) 
< 0) {
-                               char *colon = filename + (*filename ? 1 : 0);
-
-                               while ((colon = strchr(colon, ':'))) {
-                                       if (*(colon - 1) == '\\')
-                                               memmove(colon - 1, colon, 
strlen(colon) + 1);
-                                       else if (parse_line_column(colon + 1, 
&givenline, &givencol)) {
-                                               *colon = '\0';
-                                               if (stat(filename, &fileinfo) < 
0) {
-                                                       *colon++ = ':';
-                                                       givencol = 0;
-                                               }
-                                       } else
-                                               ++colon;
+                               char *coda = filename + strlen(filename);
+  maybe_two:
+                               while (--coda > filename + 1 && ('0' <= *coda 
&& *coda <= '9'))
+                                       ;
+                               if (*coda == ':' && ('0' <= *(coda + 1) && 
*(coda +1) <= '9')) {
+                                       *coda = '\0';
+                                       if (stat(filename, &fileinfo) < 0) {
+                                               *coda = ':';
+                                               /* If this was the first colon, 
look for a second one. */
+                                               if (!strchr(coda + 1, ':'))
+                                                       goto maybe_two;
+                                       } else if (!parse_line_column(coda + 1, 
&givenline, &givencol))
+                                               die(_("Invalid number\n"));
                                }
                        }
 
-- 
2.42.1