runtime(tar): improve the error detection

Do not rely on the fact, that the last line matches warning, error,
inappropriate or unrecognized to determine if an error occurred. It
could also be a file, contains such a keyword.

So make the error detection slightly more strict and only assume an
error occured, if in addition to those 4 keywords, also a space matches
(this assumes the error message contains a space), which luckily on Unix
not many files match by default.

The whole if condition seems however slightly dubious.  In case an error
happened, this would probably already be caught in the previous if
statement, since this checks for the return code of the tar program.

There may however be tar implementations, that do not set the exit code
for some kind of error (but print an error message)? But let's keep this
check for now, not many people have noticed this behaviour until now, so
it seems to work reasonably well anyhow.

related: #6425
fixes: #13489
Signed-off-by: Christian Brabandt <[email protected]>

Author: chrisbra

runtime/autoload/tar.vim

@@ -1,7 +1,7 @@
 " tar.vim: Handles browsing tarfiles
 "            AUTOLOAD PORTION
-" Date:		Jan 07, 2020
-" Version:	32
+" Date:		Nov 05, 2023
+" Version:	32a  (with modifications from the Vim Project)
 " Maintainer:	Charles E Campbell <[email protected]>
 " License:	Vim License  (see vim's :help license)
 "
@@ -22,7 +22,7 @@
 if &cp || exists("g:loaded_tar")
  finish
 endif
-let g:loaded_tar= "v32"
+let g:loaded_tar= "v32a"
 if v:version < 702
  echohl WarningMsg
  echo "***warning*** this version of tar needs vim 7.2"
@@ -208,7 +208,16 @@ fun! tar#Browse(tarfile)
 "   call Dret("tar#Browse : a:tarfile<".a:tarfile.">")
    return
   endif
-  if line("$") == curlast || ( line("$") == (curlast + 1) && getline("$") =~# '\c\%(warning\|error\|inappropriate\|unrecognized\)')
+  " If there was an error message, the last line probably matches some keywords but
+  " should also contain whitespace for readability. Make sure not to match a
+  " filename that contains the keyword (error/warning/unrecognized/inappropriate, etc)
+  "
+  " FIXME:is this actually necessary? In case of an error, we should probably
+  "       have noticed in the if statement above since tar should have exited
+  "       with a non-zero exit code.
+  if line("$") == curlast || ( line("$") == (curlast + 1) &&
+        \ getline("$") =~# '\c\<\%(warning\|error\|inappropriate\|unrecognized\)\>' &&
+        \ getline("$") =~  '\s' )
    redraw!
    echohl WarningMsg | echo "***warning*** (tar#Browse) ".a:tarfile." doesn't appear to be a tar file" | echohl None
    keepj sil! %d