# dpkg manual page - dpkg-mergechangelogs(1)
#
# Copyright © 2009-2010 Raphaël Hertzog <hertzog@debian.org>
#
# This is free software; you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation; either version 2 of the License, or
# (at your option) any later version.
#
# This is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <https://www.gnu.org/licenses/>.

=encoding utf8

=head1 NAME

dpkg-mergechangelogs - 3-way merge of debian/changelog files

=head1 SYNOPSIS

B<dpkg-mergechangelogs>
[I<option>...] I<old> I<new-a> I<new-b> [I<out>]

=head1 DESCRIPTION

This program will use the 3 provided versions of the Debian changelog to
generate a merged changelog file.
The resulting changelog is stored
in the file I<out> or output to the standard output if that parameter is
not given.

Each entry is identified by its version number and they are assumed to
be not conflicting, they are simply merged in the right order (by
decreasing version number).
When B<--merge-prereleases> is used, the
part of the version number after the last tilde is dropped so that
1.0-1~exp1 and 1.0-1~exp5 are considered to be the same entry.
When the
same version is available in both I<new-a> and I<new-b>, a standard
line-based 3-way merge is attempted (provided that the module
Algorithm::Merge is available — it's part of the package
libalgorithm-merge-perl — otherwise you get a global conflict on the
content of the entry).

This program was introduced in dpkg 1.15.7.

=head1 OPTIONS

=over

=item B<--merge-unreleased>

Ignore the version number when the entries are marked as B<UNRELEASED>
(since dpkg 1.21.0).

This is useful when you have diverging development for versions that have
not yet been released.
For instance 2.1-1 is released, then development
happens for the new 2.2-1 and then for 2.3-1, where it makes sense to just
end with a coalesced entry for 2.3-1 including all the development done in
2.2-1.

=item B<-m>, B<--merge-prereleases>

Drop the part after the last tilde in the version number when doing
version comparison to identify if two entries are supposed to be
the same or not.

This is useful when you keep using the same changelog entry but you
increase its version number regularly.
For instance, you might have
2.3-1~exp1, 2.3-1~exp2, ... until the official release 2.3-1 and they
are all the same changelog entry that has evolved over time.

=item B<--help>

Show the usage message and exit.

=item B<--version>

Show the version and exit.

=back

=head1 ENVIRONMENT

=over

=item B<DPKG_COLORS>

Sets the color mode (since dpkg 1.18.5).
The currently accepted values are: B<auto> (default), B<always> and
B<never>.

=item B<DPKG_NLS>

If set, it will be used to decide whether to activate Native Language Support,
also known as internationalization (or i18n) support (since dpkg 1.19.0).
The accepted values are: B<0> and B<1> (default).

=back

=head1 LIMITATIONS

Anything that is not parsed by L<Dpkg::Changelog> is lost during the merge.
This might include stuff like comments which were not supposed to be
there, etc.

=head1 INTEGRATION WITH GIT

If you want to use this program to merge Debian changelog files in a git
repository, you have first to register a new merge driver in
B<.git/config> or B<~/.gitconfig>:

 [merge "dpkg-mergechangelogs"]
    name = debian/changelog merge driver
    driver = dpkg-mergechangelogs -m %O %A %B %A

Then you have to setup the merge attribute for the debian/changelog file
either in B<.gitattributes> in the repository itself, or in
B<.git/info/attributes>:

 debian/changelog merge=dpkg-mergechangelogs
