[[updating]]
== Updating Erlang.mk

This chapter describes how to update the 'erlang.mk' file
in your repository.

=== Initial bootstrap

The first time you use Erlang.mk, it will bootstrap itself.
It always uses the most recent version for this, so you don't
have to update after creating your project.

=== Updating

Later on though, updating becomes a necessity. Erlang.mk
developers and contributors relentlessly improve the project
and add new features; it would be a waste not to benefit
from this.

That's why updating Erlang.mk is so simple. All you need
to do is to call `make erlang-mk`:

[source,bash]
----
$ make erlang-mk
git clone https://github.com/ninenines/erlang.mk .erlang.mk.build
Cloning into '.erlang.mk.build'...
remote: Counting objects: 4035, done.
remote: Compressing objects: 100% (12/12), done.
remote: Total 4035 (delta 8), reused 4 (delta 4), pack-reused 4019
Receiving objects: 100% (4035/4035), 1.10 MiB | 1000.00 KiB/s, done.
Resolving deltas: 100% (2442/2442), done.
Checking connectivity... done.
if [ -f build.config ]; then cp build.config .erlang.mk.build; fi
cd .erlang.mk.build && make
make[1]: Entering directory '/home/essen/tmp/emkg/hello_joe/.erlang.mk.build'
awk 'FNR==1 && NR!=1{print ""}1' core/core.mk index/*.mk core/index.mk core/deps.mk plugins/protobuffs.mk core/erlc.mk core/docs.mk core/test.mk plugins/asciidoc.mk plugins/bootstrap.mk plugins/c_src.mk plugins/ci.mk plugins/ct.mk plugins/dialyzer.mk plugins/edoc.mk plugins/elvis.mk plugins/erlydtl.mk plugins/escript.mk plugins/eunit.mk plugins/relx.mk plugins/shell.mk plugins/triq.mk plugins/xref.mk plugins/cover.mk \
	| sed 's/^ERLANG_MK_VERSION = .*/ERLANG_MK_VERSION = 1.2.0-642-gccd2b9f/' > erlang.mk
make[1]: Leaving directory '/home/essen/tmp/emkg/hello_joe/.erlang.mk.build'
cp .erlang.mk.build/erlang.mk ./erlang.mk
rm -rf .erlang.mk.build
----

All that's left to do is to commit the file!

Yep, it's that easy.

=== Customizing the build

Erlang.mk allows you to customize which plugins are to be included
in the 'erlang.mk' file. You can do so by maintaining your own
'build.config' file in your repository. Erlang.mk will automatically
use it the next time you run `make erlang-mk`.

The 'build.config' file contains the list of all files that will
be built into the resulting 'erlang.mk' file. You can start from
the https://github.com/ninenines/erlang.mk/blob/master/build.config[most recent version]
and customize to your needs.

You can also name the file differently or put it in a separate folder
by modifying the value for `ERLANG_MK_BUILD_CONFIG`. You can also
tell Erlang.mk to use a different temporary directory by changing
the `ERLANG_MK_BUILD_DIR` variable.