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, 4 insertions, 4 deletions

diff --git a/test/integration/test-apt-patterns b/test/integration/test-apt-patterns
index b091c8729..33df21d36 100755
--- a/test/integration/test-apt-patterns
+++ b/test/integration/test-apt-patterns
@@ -256,10 +256,10 @@ E: Unmet dependencies. Try 'apt --fix-broken install' with no packages (or speci
 
 # other wildcards should fail
 
-# FIXME: This should fail
-testsuccessequal "Listing...
-automatic1/now 1.0 i386 [installed,local]
-automatic2/now 1.0 i386 [installed,local]" apt list 'automatic?'
+testfailureequal "Listing...
+E: input:0-10: error: Expected pattern
+   automatic?
+   ^^^^^^^^^^" apt list 'automatic?'