apt list: Fix behavior of regex vs fnmatch vs wildcards

Previously (and still in cacheset), patterns where only allowed to
start with ? or ~, which ignores the fact that a pattern might just
as well start with a negation, such a !~nfoo.

Also, we ignored the --regex flag if it looked like this, which
was somewhat bad.

Let's change this all:

* If --regex is given, arguments are always interpreted as regex
* If it is a valid package wildcard (name or * characters), then
  it will be interpreted as a wildcard - this set of characters is
  free from meaningful overlap with patterns.
* Otherwise, the argument is interpreted as a pattern.

For a future version, we need to adapt parsing for cacheset and
list to use a common parser, to avoid differences in their
interpretation. Likely, this code will go into the pattern parser,
such that it generates a pattern given a valid fnmatch argument
for example.

1 files changed, 5 insertions, 4 deletions

diff --git a/apt-private/private-list.cc b/apt-private/private-list.cc
index f5c31bbcd..eee657c46 100644
--- a/apt-private/private-list.cc
+++ b/apt-private/private-list.cc
@@ -39,6 +39,7 @@ struct PackageSortAlphabetic						/*{{{*/
 
 class PackageNameMatcher : public Matcher
 {
+   static constexpr const char *const isfnmatch_strict = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789+-.:*";
    pkgCacheFile &cacheFile;
   public:
    explicit PackageNameMatcher(pkgCacheFile &cacheFile, const char **patterns)
@@ -48,12 +49,12 @@ class PackageNameMatcher : public Matcher
       {
          std::string pattern = patterns[i];
          APT::CacheFilter::Matcher *cachefilter = NULL;
-	 if (pattern.size() > 0 && (pattern[0] == '?' || pattern[0] == '~'))
-	    cachefilter = APT::CacheFilter::ParsePattern(pattern, &cacheFile).release();
-         else if(_config->FindB("APT::Cmd::Use-Regexp", false) == true)
+         if(_config->FindB("APT::Cmd::Use-Regexp", false) == true)
             cachefilter = new APT::CacheFilter::PackageNameMatchesRegEx(pattern);
-         else
+         else if (pattern.find_first_not_of(isfnmatch_strict) == std::string::npos)
             cachefilter = new APT::CacheFilter::PackageNameMatchesFnmatch(pattern);
+	 else
+	    cachefilter = APT::CacheFilter::ParsePattern(pattern, &cacheFile).release();
 
          if (cachefilter == nullptr) {
             return;