=head1 Name

sqitch-revert - Revert changes to a database

=head1 Synopsis

  sqitch revert [options] [<database>]
  sqitch revert [options] [<database>] <change>
  sqitch revert [options] [<database>] --to-change <change>
  sqitch revert [options] [<database>] --modified

=head1 Description

Revert changes to the database. Starting from the current deployment state,
changes will be reverted in reverse the order of application. All changes will
be reverted unless a change is specified, either via C<--to> or with no option
flag, in which case changes will be reverted back to that change.

If the database has not been deployed to, or its state already matches the
specified change, no changes will be made. If the change appears later in the
plan than the currently-deployed state, an error will be returned, along with
a suggestion to instead use L<sqitch-deploy>.

The C<< <database> >> parameter specifies the database to which to connect,
and may also be specified as the C<--target> option. It can be target name,
a URI, an engine name, or plan file path.

=head2 Attention Git Users

If you're a git user thinking this is like C<git revert>, it's not.
C<sqitch revert> is more like time travel. It takes your database back to the
state it had just after applying the target change. It feels like magic, but
it's actually all the time you spent writing revert scripts that finally pays
off. Starting from the last change currently deployed, C<sqitch revert> runs
each revert script in turn until the target change is reached and becomes the
last change deployed.

=head1 Options

=over

=item C<-t>

=item C<--target>

The target database to which to connect. This option can be either a URI or
the name of a target in the configuration.

=item C<--to-change>

=item C<--change>

=item C<--to>

Specify the reversion change. Defaults to reverting all changes. See
L<sqitchchanges> for the various ways in which changes can be specified.

=item C<-m>

=item C<--modified>

Finds the change to revert onto based on modifications to deploy scripts. Reverts
the change prior to earliest change with a revised deploy script.

=item C<-s>

=item C<--set>

Set a variable name and value for use by the database engine client, if it
supports variables. The format must be C<name=value>, e.g.,
C<--set defuser='Homer Simpson'>. Overrides any values loaded from
L</configuration Variables>.

=item C<--log-only>

Log the changes as if they were reverted, but without actually running the
revert scripts.

=item C<--lock-timeout>

  sqitch deploy --lock-timeout 600

Set the number of seconds for Sqitch to wait to get an exclusive advisory
lock on the target database, for engines that support such a lock. This
lock prevents other instances of Sqitch from deploying to the target at the
same time, but prevents no other database activity. Defaults to 60.

=item C<-y>

Disable the prompt that normally asks whether or not to execute the revert.

=item C<--registry>

  sqitch revert --registry registry

The name of the Sqitch registry schema or database in which sqitch stores its
own data.

=item C<--db-client>

=item C<--client>

  sqitch revert --client /usr/local/pgsql/bin/psql

Path to the command-line client for the database engine. Defaults to a client
in the current path named appropriately for the database engine.

=item C<-d>

=item C<--db-name>

  sqitch revert --db-name widgets
  sqitch revert -d bricolage

Name of the database. In general, L<targets|sqitch-target> and URIs are
preferred, but this option can be used to override the database name in a
target.

=item C<-u>

=item C<--db-user>

=item C<--db-username>

  sqitch revert --db-username root
  sqitch revert --db-user postgres
  sqitch revert -u Mom

User name to use when connecting to the database. Does not apply to all
engines. In general, L<targets|sqitch-target> and URIs are preferred, but this
option can be used to override the user name in a target.

=item C<-h>

=item C<--db-host>

  sqitch revert --db-host db.example.com
  sqitch revert -h appdb.example.net

Host name to use when connecting to the database. Does not apply to all
engines. In general, L<targets|sqitch-target> and URIs are preferred, but this
option can be used to override the host name in a target.

=item C<-p>

=item C<--db-port>

  sqitch revert --db-port 7654
  sqitch revert -p 5431

Port number to connect to. Does not apply to all engines. In general,
L<targets|sqitch-target> and URIs are preferred, but this option can be used
to override the port in a target.

=item C<--plan-file>

=item C<-f>

  sqitch revert --plan-file my.plan

Path to the deployment plan file. Overrides target, engine, and core
configuration values. Defaults to F<$top_dir/sqitch.plan>.

=back

=head1 Configuration Variables

=over

=item C<[deploy.variables]>

=item C<[revert.variables]>

A section defining database client variables. The C<deploy.variables>
configuration is read from the C<deploy> command configuration, on the
assumption that the values will generally be the same on revert. If they're
not, use C<revert.variables> to override C<deploy.variables>.

These variables are useful if your database engine supports variables in
scripts, such as PostgreSQL's
L<C<psql> variables|https://www.postgresql.org/docs/current/static/app-psql.html#APP-PSQL-INTERPOLATION>,
Vertica's
L<C<vsql> variables|https://my.vertica.com/docs/7.1.x/HTML/index.htm#Authoring/ConnectingToHPVertica/vsql/Variables.htm>,
MySQL's
L<user variables|https://dev.mysql.com/doc/refman/5.6/en/user-variables.html>,
SQL*Plus's
L<C<DEFINE> variables|https://docs.oracle.com/cd/B19306_01/server.102/b14357/ch12017.htm>,
and Snowflake's
L<SnowSQL variables|https://docs.snowflake.com/en/user-guide/snowsql-use.html#using-variables>.

May be overridden by C<--set> or target and engine configuration. Variables
are merged in the following priority order:

=over

=item C<--set>

=item C<target.$target.variables>

=item C<engine.$engine.variables>

=item C<revert.variables>

=item C<deploy.variables>

=item C<core.variables>

=back

=item C<revert.strict>

A boolean value indicating whether or not the change to revert to must
be specified.

=item C<[revert.no_prompt]>

A boolean value indicating whether or not to disable the prompt before
executing the revert. May be overridden by C<-y>.

=item C<[revert.prompt_accept]>

A boolean value indicating whether default reply to the prompt before
executing the revert should be "yes" or "no". Defaults to true, meaning to
accept the revert.

=back

=head1 Sqitch

Part of the L<sqitch> suite.
