NAME
    Dist::Zilla::Plugin::ChangelogFromGit - Write a Changes file from a
    project's git log.

VERSION
    version 0.006

SYNOPSIS
    Here's an example dist.ini section showing all the current options and
    their default values.

            [ChangelogFromGit]
            max_age     = 365
            tag_regexp  = ^v(\d+\.\d+)$
            file_name   = CHANGES
            wrap_column = 74
            debug       = 0

    Variables don't need to be set to their default values. This is
    equivalent to the configuration above.

            [ChangelogFromGit]

DESCRIPTION
    This Dist::Zilla plugin turns a project's git commit log into a change
    log file. It's better than simply running `git log > CHANGES` in at
    least two ways. First, it understands release tags, and it uses them to
    group changes by release. Second, it reformats the changes to make them
    easier to read. And third, subclasses can change some or all of the
    reformatting to make change logs even easier to read.

    See this project's CHANGES file for sample output. Yes, this project
    uses itself to generate its own change log. Why not?

CONFIGURATION / PUBLIC ATTRIBUTES
    As seen in the "SYNOPSIS", this plugin has a number of public attributes
    that may be set using dist.ini configuration variables.

  max_age = INTEGER
    The "max_age" configuration variable limits the age of releases to be
    included in the change log. The default is to include releases going
    back about a year. To include about two years, one would double the
    default value:

            [ChangelogFromGit]
            max_age = 730

    "max_age" is intended to limit the size of change logs for large,
    long-term projects that don't want to include the entire, huge commit
    history in every release.

  tag_regexp = REGULAR_EXPRESSION
    "tag_regexp" sets the regular expression that detects which tags mark
    releases. It also extracts the version numbers from these tags using a
    regular expression back reference or capture. For example, a project's
    release tags might match 'release-1.000', 'release-1.001', etc. This
    "tag_regexp" will find them and extract their versions.

            [ChangelogFromGit]
            tag_regexp = ^release-(\d+.*)$

    There is no single standard format for release tags. "tag_regexp"
    defaults to the author's convention. It will most likely need to be
    changed.

  file_name = STRING
    "file_name" sets the name of the change log that will be written. It
    defaults to "CHANGES", but some people may prefer "Changes",
    "Changelog", or something else.

            [ChangelogFromGit]
            file_name = Changes

  wrap_column = INTEGER
    Different contributors tend to use different commit message formats,
    which can be disconcerting to the typographically aware release
    engineer. "wrap_column" sets the line length to which all commit
    messages will be re-wrapped. It's 74 columns by default. If this is too
    short:

            [ChangelogFromGit]
            wrap_column = 78

  debug = BOOLEAN
    Developers are people, too. The "debug" option enables some noisy
    runtime tracing on STDERR.

            [ChangelogFromGit]
            debug = 1

  exclude_message = REGULAR_EXPRESSION
    "exclude_message" sets a regular expression which discards matching
    commit messages. This provides a way to exclude commit messages such as
    'forgot to include file X' or 'typo'. The regular expression is case
    sensitive.

            [ChangelogFromGit]
            exclude_message = ^(forgot|typo)

    "include_message" can be used to do the opposite: exclude all changes
    except ones that match a regular expression. Using both at once is
    liable to generate empty change logs.

  include_message = REGULAR_EXPRESSION
    "include_message" does the opposite of "exclude_message": it sets a
    regular expression which commit messages must match in order to be
    included in the Changes file. This means that when making a commit with
    a relevant message, you must include text that matches the regular
    expression pattern to have it included in the Changes file. All other
    commit messages are ignored.

    The regular expression is case sensitive.

            [ChangelogFromGit]
            include_message = ^Major

    Using both "include_message" and "exclude_message" at the same time will
    most likely result in empty change logs.

HOW IT WORKS
    Dist::Zilla::ChangelogFromGit collects the tags matching "tag_regexp"
    that are not older than "max_age" days old. These are used to identify
    and time stamp releases. Each release is encapsulated into a
    Software::Release object.

    Git::Repository::Log::Iterator is used to collect the changes prior to
    each release but after the previous release. Change log entries are
    added to their respective Software::Release objects.

    "$self->render_changelog()" is called after all the relevant releases
    and changes are known. It must return the rendered change log as a
    string. That string will be used as the content for a
    Dist::Zilla::File::InMemory object representing the new change log.

SUBCLASSING FOR NEW FORMATS
    Dist::Zilla::ChangelogFromGit implement about a dozen methods to render
    the various parts of a change log. Subclasses may override or augment
    any or all of these methods to alter the way change logs are rendered.

    All methods beginning with "render" return strings that will be
    incorporated into the change log. Methods that will not contribute to
    the change log must return empty strings.

  Rendering Entire Change Logs
    Methods beginning with "render_changelog" receive no parameters other
    than $self. Everything they need to know about the change log is
    included in the object's attributes: "wrap_column", "releases",
    "skipped_release_count", "earliest_date".

   render_changelog
    render_changelog() returns the text of the entire change log. By
    default, the change log is built from a header, zero or more releases,
    and a footer.

            sub render_changelog {
                    my $self = shift();
                    return(
                            $self->render_changelog_header() .
                            $self->render_changelog_releases() .
                            $self->render_changelog_footer()
                    );
            }

   render_changelog_header
    render_changelog_header() renders some text that introduces the reader
    to the change log.

            sub render_changelog_header {
                    my $self = shift();
                    my $header = (
                            "Changes from " . $self->format_datetime($self->earliest_date()) .
                            " to present."
                    );
                    return $self->surround_line("=", $header) . "\n";
            }

   render_changelog_releases
    render_changelog_releases() iterates through each release, calling upon
    $self to render them one at a time.

            sub render_changelog_releases {
                    my $self = shift();

                    my $changelog = '';

                    RELEASE: foreach my $release (reverse $self->all_releases()) {
                            next RELEASE if $release->has_no_changes();
                            $changelog .= $self->render_release($release);
                    }

                    return $changelog;
            }

   render_changelog_footer
    render_changelog_footer() tells the reader that the change log is over.
    Normally the end of the file is sufficient warning, but a truncated
    change log is friendlier when the reader knows what they're missing.

            sub render_changelog_footer {
                    my $self = shift();

                    my $skipped_count = $self->skipped_release_count();

                    my $changelog_footer;

                    if ($skipped_count) {
                            my $releases = "release" . ($skipped_count == 1 ? "" : "s");
                            $changelog_footer = (
                                    "Plus $skipped_count $releases after " .
                                    $self->format_datetime($self->earliest_date()) . '.'
                            );
                    }
                    else {
                            $changelog_footer = "End of releases.";
                    }

                    return $self->surround_line("=", $changelog_footer);
            }

  Rendering Individual Releases
    Methods beginning with "render_release" receive $self plus one
    additional parameter: a Software::Release object encapsulating the
    release and its changes. See Software::Release to learn the information
    that object encapsulates.

   render_release
    render_release() is called upon to render a single release. In the
    change log, a release consists of a header, one or more changes, and a
    footer.

            sub render_release {
                    my ($self, $release) = @_;
                    return(
                            $self->render_release_header($release) .
                            $self->render_release_changes($release) .
                            $self->render_release_footer($release)
                    );
            }

   render_release_header
    render_release_header() introduces a release.

            sub render_release_header {
                    my ($self, $release) = @_;

                    my $version = $release->version();
                    $version = $self->zilla()->version() if $version eq 'HEAD';

                    my $release_header = (
                            $self->format_release_tag($release->version()) . ' at ' .
                            $self->format_datetime($release->date())
                    );

                    return $self->surround_line("-", $release_header) . "\n";
            }

   render_release_changes
    render_release_changes() iterates through the changes associated with
    each Software::Release object. It calls upon render_change() to render
    each change.

            sub render_release_changes {
                    my ($self, $release) = @_;

                    my $changelog = '';

                    foreach my $change (@{ $release->changes() }) {
                            $changelog .= $self->render_change($release, $change);
                    }

                    return $changelog;
            }

   render_release_footer
    render_release_footer() may be used to divide releases. It's not used by
    default, but it's implemented for completeness.

            sub render_release_footer {
                    my ($self, $release) = @_;
                    return '';
            }

  Rendering Individual Changes
    Methods beginning with "render_change" receive two parameters in
    addition to $self: a Software::Release object encapsulating the release
    containing this change, and a Software::Release::Change object
    encapsulating the change itself.

   render_change
    render_change() renders a single change, which is the catenation of a
    change header, change message, and footer.

            sub render_change {
                    my ($self, $release, $change) = @_;
                    return(
                            $self->render_change_header($release, $change) .
                            $self->render_change_message($release, $change) .
                            $self->render_change_footer($release, $change)
                    );
            }

   render_change_header
    render_change_header() generally renders identifying information about
    each change. This method's responsibility is to produce useful
    information in a pleasant format.

            sub render_change_header {
                    my ($self, $release, $change) = @_;

                    use Text::Wrap qw(fill);

                    local $Text::Wrap::huge    = 'wrap';
                    local $Text::Wrap::columns = $self->wrap_column();

                    my @indent = ("  ", "  ");

                    return(
                            fill(
                                    "  ", "  ",
                                    'Change: ' . $change->change_id
                            ) .
                            "\n" .
                            fill(
                                    "  ", "  ",
                                    'Author: ' . $change->author_name.' <'.$change->author_email.'>'
                            ) .
                            "\n" .
                            fill(
                                    "  ", "  ",
                                    'Date  : ' . $self->format_datetime($change->date())
                            ) .
                            "\n\n"
                    );
            }

   render_change_message
    render_change_message() renders the commit message for the change log.

            sub render_change_message {
                    my ($self, $release, $change) = @_;

                    use Text::Wrap qw(fill);

                    return '' if $change->description() =~ /^\s/;

                    local $Text::Wrap::huge = 'wrap';
                    local $Text::Wrap::columns = $self->wrap_column();

                    return fill("    ", "    ", $change->description) . "\n";
            }

   render_change_footer
    render_change_footer() returns summary and/or divider text for the
    change.

            sub render_change_footer {
                    my ($self, $release, $change) = @_;
                    return "\n";
            }

  Formatting Data
    Dist::Zilla::Plugin::ChangelogFromGit includes a few methods to
    consistently format certain data types.

   format_datetime
    format_datetime() converts the DateTime objects used internally into
    friendly, human readable dates and times for the change log.

            sub format_datetime {
                    my ($self, $datetime) = @_;
                    return $datetime->strftime("%F %T %z");
            }

   format_release_tag
    format_release_tag() turns potentially cryptic release tags into
    friendly version numbers for the change log. By default, it also
    replaces the 'HEAD' version with the current version being released.
    This accommodates release managers who prefer to tag their distributions
    after releasing them.

            sub format_release_tag {
                    my ($self, $release_tag) = @_;

                    return 'version ' . $self->zilla()->version() if $release_tag eq 'HEAD';

                    my $tag_regexp = $self->tag_regexp();
                    $release_tag =~ s/$tag_regexp/version $1/;
                    return $release_tag;
            }

   surround_line
    surround_line() will surround a line of output with lines of dashes or
    other characters. It's used to help heading stand out. This method takes
    two strings: a character (or string) that will repeat to fill
    surrounding lines, and the line to surround. It returns a three-line
    string: the original line preceded and followed by surrounding lines.

            sub surround_line {
                    my ($self, $character, $string) = @_;

                    my $surrounder = substr(
                            ($character x (length($string) / length($character) + 1)),
                            0,
                            length($string)
                    );

                    return "$surrounder\n$string\n$surrounder\n";
            }

INTERNAL ATTRIBUTES
    Dist::Zilla::Plugin::ChangelogFromGit accumulates useful information
    into a few internal attributes. These aren't intended to be configured
    by dist.ini, but they are important for rendering change logs.

  earliest_date
    earliest_date() contains a DateTime object that represents the date and
    time of the earliest release to include. It's initialized as midnight
    for the date max_age() days ago.

  releases
    releases() contains an array reference of Software::Release objects that
    will be included in the change log.

   all_releases
    all_releases() returns a list of the Software::Release objects that
    should be included in the change log. It's a friendly equivalent of
    "@{$self->releases()}".

   get_release
    get_release() returns a single release by index. The first release in
    the change log may be retrieved as "$self->get_release(0)".

   releae_count
    release_count() returns the number of Software::Release objects in the
    "releases" attribute.

   sort_releases
    sort_releases() sorts the Software::Release objects in the releases()
    using some comparator. For example, to sort releases in time order:

            $self->sort_releases(
                    sub {
                            DateTime->compare( $_[0]->date(), $_[1]->date() )
                    }
            );

  skipped_release_count
    skipped_release_count() contains the number of releases truncated by
    max_age(). The default render_changelog_footer() uses it to display the
    number of changes that have been omitted from the log.

Subversion and CVS
    This plugin is almost entirely a copy-and-paste port of a command-line
    tool I wrote a while ago. I also have tools to generate similar change
    logs for CVS and Subversion projects. I'm happy to contribute that code
    to people interested in creating Dist::Zilla plugins for other version
    control systems.

    We should also consider abstracting the formatting code out to a role so
    that it can be shared among different plugins.

BUGS
    The documentation includes copies of the renderer methods. This
    increases technical debt, since changes to those methods must also be
    copied into the documentation. Rocco needs to finish Pod::Plexus and use
    it here to simplify maintenance of the documentation.

    Collecting all releases and changes before rendering the change log may
    be considered harmful for extremely large projects. If someone thinks
    they can generate change logs incrementally, their assistance would be
    appreciated.

AUTHORS
    Rocco Caputo <rcaputo@cpan.org> - Initial release, and ongoing
    management and maintenance.

    Cory G. Watson <gphat@cpan.org> - Made formatting extensible and
    overridable.

COPYRIGHT AND LICENSE
    This software is copyright (c) 2010-2011 by Rocco Caputo.

    This is free software; you may redistribute it and/or modify it under
    the same terms as the Perl 5 programming language itself.

