Do major refactor of format code

This gets rid of a lot of duplicated logic that was previously
copy&pasted. This commit alos:
- Makes it easier to implement new formats
- Gets rid of a few bugs
- Makes the system more flexible (more options)
- Adds a lot of additional tests

tests/format-output/1-default.toml

@@ -5,7 +5,6 @@
 # Required! This value must be specified.
 #site_name =
 
-
 # Configurations related to the HTTP communication.
 [http]
 # The port the server will listen on.
@@ -21,7 +20,6 @@
 # Default value: "127.0.0.1"
 #bind = "127.0.0.1"
 
-
 [http.headers]
 # The header in which the reverse proxy specifies the username.
 #
@@ -33,7 +31,6 @@
 # Default value: "x-display-name"
 #display_name = "x-display-name"
 
-
 # Configuring the logging.
 [log]
 # If set to `true`, the app will log to stdout.

tests/format-output/1-default.yaml

@@ -14,6 +14,12 @@ http:
   # Required! This value must be specified.
   #port:
 
+  # The bind address of the server. Can be set to `0.0.0.0` for example, to
+  # allow other users of the network to access the server.
+  #
+  # Default value: 127.0.0.1
+  #bind: 127.0.0.1
+
   headers:
     # The header in which the reverse proxy specifies the username.
     #
@@ -25,12 +31,6 @@ http:
     # Default value: x-display-name
     #display_name: x-display-name
 
-  # The bind address of the server. Can be set to `0.0.0.0` for example, to
-  # allow other users of the network to access the server.
-  #
-  # Default value: 127.0.0.1
-  #bind: 127.0.0.1
-
 # Configuring the logging.
 log:
   # If set to `true`, the app will log to stdout.

tests/format-output/1-indent-2.toml

@@ -0,0 +1,43 @@
+# A sample configuration for our app.
+
+# Name of the website.
+#
+# Required! This value must be specified.
+#site_name =
+
+  # Configurations related to the HTTP communication.
+  [http]
+  # The port the server will listen on.
+  #
+  # Can also be specified via environment variable `PORT`.
+  #
+  # Required! This value must be specified.
+  #port =
+
+  # The bind address of the server. Can be set to `0.0.0.0` for example, to
+  # allow other users of the network to access the server.
+  #
+  # Default value: "127.0.0.1"
+  #bind = "127.0.0.1"
+
+    [http.headers]
+    # The header in which the reverse proxy specifies the username.
+    #
+    # Default value: "x-username"
+    #username = "x-username"
+
+    # The header in which the reverse proxy specifies the display name.
+    #
+    # Default value: "x-display-name"
+    #display_name = "x-display-name"
+
+  # Configuring the logging.
+  [log]
+  # If set to `true`, the app will log to stdout.
+  #
+  # Default value: true
+  #stdout = true
+
+  # If this is set, the app will write logs to the given file. Of course,
+  # the app has to have write access to that file.
+  #file =

tests/format-output/1-nested-gap-2.toml

@@ -0,0 +1,46 @@
+# A sample configuration for our app.
+
+# Name of the website.
+#
+# Required! This value must be specified.
+#site_name =
+
+
+# Configurations related to the HTTP communication.
+[http]
+# The port the server will listen on.
+#
+# Can also be specified via environment variable `PORT`.
+#
+# Required! This value must be specified.
+#port =
+
+# The bind address of the server. Can be set to `0.0.0.0` for example, to
+# allow other users of the network to access the server.
+#
+# Default value: "127.0.0.1"
+#bind = "127.0.0.1"
+
+
+[http.headers]
+# The header in which the reverse proxy specifies the username.
+#
+# Default value: "x-username"
+#username = "x-username"
+
+# The header in which the reverse proxy specifies the display name.
+#
+# Default value: "x-display-name"
+#display_name = "x-display-name"
+
+
+# Configuring the logging.
+[log]
+# If set to `true`, the app will log to stdout.
+#
+# Default value: true
+#stdout = true
+
+# If this is set, the app will write logs to the given file. Of course,
+# the app has to have write access to that file.
+#file =

tests/format-output/1-no-comments.yaml

@@ -1,10 +1,13 @@
 #site_name:
+
 http:
   #port:
+  #bind: 127.0.0.1
+
   headers:
     #username: x-username
     #display_name: x-display-name
-  #bind: 127.0.0.1
+
 log:
   #stdout: true
   #file:

tests/format-output/2-default.toml

@@ -0,0 +1,23 @@
+# A sample configuration for our app.
+
+[http]
+[http.headers]
+# The header in which the reverse proxy specifies the username.
+#
+# Default value: "x-username"
+#username = "x-username"
+
+# The header in which the reverse proxy specifies the display name.
+#
+# Default value: "x-display-name"
+#display_name = "x-display-name"
+
+[http.log]
+# If set to `true`, the app will log to stdout.
+#
+# Default value: true
+#stdout = true
+
+# If this is set, the app will write logs to the given file. Of course,
+# the app has to have write access to that file.
+#file =

tests/format-output/2-default.yaml

@@ -0,0 +1,23 @@
+# A sample configuration for our app.
+
+http:
+  headers:
+    # The header in which the reverse proxy specifies the username.
+    #
+    # Default value: x-username
+    #username: x-username
+
+    # The header in which the reverse proxy specifies the display name.
+    #
+    # Default value: x-display-name
+    #display_name: x-display-name
+
+  log:
+    # If set to `true`, the app will log to stdout.
+    #
+    # Default value: true
+    #stdout: true
+
+    # If this is set, the app will write logs to the given file. Of course,
+    # the app has to have write access to that file.
+    #file: