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Rocco Caputo


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


version 0.017


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

        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.



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?


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:

        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.

min_releases = INTEGER

min_releases sets the minimum number of releases that should be included. It defaults to 1 so that at least the current release is added, regardless of max_age.

        min_releases = 5

max_releases = INTEGER

c<max_releases> allows you limit the number of releases included. max_age will still be the limiting factor if it contains fewer releases than the max specified.

        max_releases = 15


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.

        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.

        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:

        wrap_column = 78

debug = BOOLEAN

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

        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.

        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.

        include_message = ^Major

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


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.


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() 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();
                        $self->render_changelog_header() .
                        $self->render_changelog_releases() .


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() 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() 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() 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) = @_;
                        $self->render_release_header($release) .
                        $self->render_release_changes($release) .


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 ' .

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


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

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


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 = ("  ", "  ");

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


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() 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() 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() 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() 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)),

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


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


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


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


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

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


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.


Dist::Zilla::Plugin::ChangelogFromGit implements a couple of "unpublished" methods. These are not intended for general use.


Find all release tags back to the earliest changelog date.

Add a virtual release for the most recent change in the repository. This lets us include changes after the last releases, up to "HEAD".


A wrapper to run git commands.

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.


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.


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

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


This software is copyright (c) 2010-2018 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.