git: implement date_parse method

Users are expected to be familiar with git's "approxidate"
functionality for parsing dates, so we'll expose that
in our UIs.  Xapian itself has limited date parsing functionality
and I can't expect users to learn it.

This takes around 4-5ms on my aging workstation, so it'll
probably be made acceptable for the WWW UI, even.

libgit2 has a git__date_parse function which I expect to have
less overhead, but it's only for internal use at the moment.

1 files changed, 13 insertions, 2 deletions

diff --git a/t/git.t b/t/git.t
index 0c85e492..7b950d88 100644
--- a/t/git.t
+++ b/t/git.t
@@ -1,12 +1,11 @@
 # Copyright (C) 2015-2021 all contributors <meta@public-inbox.org>
 # License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
 use strict;
-use warnings;
 use Test::More;
 use PublicInbox::TestCommon;
 my ($dir, $for_destroy) = tmpdir();
-use PublicInbox::Spawn qw(popen_rd);
 use PublicInbox::Import;
+use POSIX qw(strftime);
 
 use_ok 'PublicInbox::Git';
 
@@ -19,6 +18,18 @@ use_ok 'PublicInbox::Git';
         xsys([qw(git fast-import --quiet)], { GIT_DIR => $dir }, $rdr);
         is($?, 0, 'fast-import succeeded');
 }
+{
+        my $git = PublicInbox::Git->new($dir);
+        my $s = $git->date_parse('1970-01-01T00:00:00Z');
+        is($s, 0, 'parsed epoch');
+        local $ENV{TZ} = 'UTC';
+        $s = $git->date_parse('1993-10-02 01:02:09');
+        is(strftime('%Y-%m-%dT%H:%M:%SZ', gmtime($s)), '1993-10-02T01:02:09Z',
+                'round trips');
+        $s = $git->date_parse('1993-10-02');
+        is(strftime('%Y-%m-%d', gmtime($s)), '1993-10-02',
+                'round trips date-only');
+}
 
 {
         my $gcf = PublicInbox::Git->new($dir);