tests/test-convert-authormap.t

match: introduce boolean prefix() method

tl;dr: This is another step towards a (previously unstated) goal of
eliminating match.files() in conditions.

There are four types of matchers:

 * always: Matches everything, checked with always(), files() is empty

 * exact: Matches exact set of files, checked with isexact(), files()
   contains the files to match

 * patterns: Matches more complex patterns, checked with anypats(),
   files() contains roots of the matched patterns

 * prefix: Matches simple 'path:' patterns as prefixes ('foo' matches
   both 'foo' and 'foo/bar'), no single method to check, files()
   contains the prefixes to match

For completeness, it would be nice to have a method for checking for
the "prefix" type of matcher as well, so let's add that, making it
return True simply when none of the others do.

The larger goal here is to eliminate uses of match.files() in
conditions (i.e. bool(match.files())). The reason for this is that
there are scenarios when you would like to create a "prefix" matcher
that happens to match no files. One example is for 'hg files -I foo
bar'. The narrowmatcher also restricts the set of files given and it
would not surprise me if have bugs caused by that already. Note that
'if m.files() and not m.anypats()' and similar is sometimes used to
catch the "exact" and "prefix" cases above.

  $ cat >> $HGRCPATH <<EOF
  > [extensions]
  > convert=
  > EOF

Prepare orig repo

  $ hg init orig
  $ cd orig
  $ echo foo > foo
  $ HGUSER='user name' hg ci -qAm 'foo'
  $ cd ..

Explicit --authors

  $ cat > authormap.txt <<EOF
  > user name = Long User Name
  > 
  > # comment
  > this line is ignored
  > EOF
  $ hg convert --authors authormap.txt orig new
  initializing destination new repository
  ignoring bad line in author map file authormap.txt: this line is ignored
  scanning source...
  sorting...
  converting...
  0 foo
  writing author map file $TESTTMP/new/.hg/authormap (glob)
  $ cat new/.hg/authormap
  user name=Long User Name
  $ hg -Rnew log
  changeset:   0:d89716e88087
  tag:         tip
  user:        Long User Name
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     foo
  
  $ rm -rf new

Implicit .hg/authormap

  $ hg init new
  $ mv authormap.txt new/.hg/authormap
  $ hg convert orig new
  ignoring bad line in author map file $TESTTMP/new/.hg/authormap: this line is ignored (glob)
  scanning source...
  sorting...
  converting...
  0 foo
  $ hg -Rnew log
  changeset:   0:d89716e88087
  tag:         tip
  user:        Long User Name
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     foo