Add docs on config file

app/views/docs/_docs_topics.html.slim

@@ -5,5 +5,6 @@ h2 Docs
   = categories.link_to 'Getting started', docs_path('getting-started'), :'getting-started'
   = categories.link_to 'Installation', docs_path(:installation), :installation
   = categories.link_to 'Usage', docs_path(:usage), :usage
+  = categories.link_to 'Configuration file', docs_path(:config), :config
   = categories.link_to 'Embedding', docs_path(:embedding), :embedding
   = categories.link_to 'FAQ', docs_path(:faq), :faq

app/views/docs/config.html.md

@@ -0,0 +1,49 @@
+<% content_for(:title, 'Configuration file') %>
+
+# Configuration file
+
+asciinema uses a config file to keep API token and user settings. In most cases
+the location of this file is `$HOME/.config/asciinema/config`.
+
+When you first run `asciinema`, local API token is generated and saved in the
+file (unless the file already exists). It looks like this:
+
+    [api]
+    token = d5a2dce4-173f-45b2-a405-ac33d7b70c5f
+
+There are several options you can set in this file. Here's a config with all
+available options set:
+
+    [api]
+    token = d5a2dce4-173f-45b2-a405-ac33d7b70c5f
+    url = https://asciinema.example.com
+
+    [record]
+    command = /bin/bash -l
+    maxwait = 2
+    yes = true
+
+    [play]
+    maxwait = 1
+
+The options in `[api]` section are related to API location and authentication.
+To tell asciinema recorder to use your own asciinema site instance rather than
+the default one (asciinema.org), you can set `url` option. API URL can also be
+passed via `ASCIINEMA_API_URL` environment variable.
+
+The options in `[record]` and `[play]` sections have the same meaning as the
+options you pass to `asciinema rec`/`asciinema play` command. If you happen to
+often use either `-c`, `-w` or `-y` with these commands then consider saving it
+as a default in the config file.
+
+## Configuration file locations
+
+In fact, the following locations are checked for the presence of the config
+file (in the given order):
+
+* `$ASCIINEMA_CONFIG_HOME/config` - if you have set `$ASCIINEMA_CONFIG_HOME`
+* `$XDG_CONFIG_HOME/asciinema/config` - on Linux, `$XDG_CONFIG_HOME` usually points to `$HOME/.config/`
+* `$HOME/.config/asciinema/config` - in most cases it's here
+* `$HOME/.asciinema/config` - created by asciinema versions prior to 1.1
+
+The first one which is found is used.

app/views/docs/usage.html.md

@@ -83,6 +83,6 @@ URL.
 NOTE: it is __necessary__ to do this if you want to __edit or delete__ your
 recordings on asciinema.org.
 
-You can synchronize your config file (which keeps the API token) across the
-machines but that's not necessary. You can assign new tokens to your account
-from as many machines as you want.
+You can synchronize your [config file](<%= docs_path(:config) %>) (which keeps
+the API token) across the machines but that's not necessary. You can assign new
+tokens to your account from as many machines as you want.