feat(man): allow arbitrary lowercase ASCII post-numeric-section suffixes

The Linux man-pages project has added `2type`, `3head`, and `3type`
recently. A web search for `man3head` gives hits for lists of sections
in the wild that are so large that we don't want to enumerate and follow
all of them.

For example, https://illumos.org/man/ lists 86 different such `man[1-9]`
categories at time of writing.

Allowing arbitrary lowercase ASCII after a numeric suffix will result in
some false positives, but seems the only maintainable option.

Closes #778

Author: scop

completions/man

@@ -6,8 +6,8 @@ _man()
     _init_completion -s -n : || return
 
     local comprsuffix=".@([glx]z|bz2|lzma|Z|zst)"
-    local manext="@([0-9lnp]|[0-9][px]|man|3?(gl|pm))?($comprsuffix)"
-    local mansect="@([0-9lnp]|[0-9][px]|3?(gl|pm))"
+    local manext="@([0-9]*([a-z])|[lnp]|man)?($comprsuffix)"
+    local mansect="@([0-9]*([a-z])|[lnp])"
 
     case $prev in
         --config-file | -!(-*)C)

test/fixtures/man/man3/bash-completion-zstd-testcase.3.zst renamed to test/fixtures/man/man3/bash-completion-zstd-testcase.3head.zst

@@ -147,5 +147,5 @@ def test_delimited_deduplication(self, completion):
         env=dict(MANPATH=manpath),
         require_cmd=True,
     )
-    def test_zstd(self, completion):
+    def test_zstd_arbitrary_sectsuffix(self, completion):
         assert completion == "e"