Add import plugin to give it docs (#2428)

* wip: add import to make it have docs

Fake the import plugin further to give it proper docs. This should help
make it more discoverable.

Signed-off-by: Miek Gieben <miek@miek.nl>

* Finish writing the documentation

Signed-off-by: Miek Gieben <miek@miek.nl>

1 files changed, 73 insertions, 0 deletions

diff --git a/plugin/import/import.md b/plugin/import/import.md
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+# import
+
+## Name
+
+*import* - include files or reference snippets from a Corefile.
+
+## Description
+
+The *import* plugin can be used to incude files into the main configuration. Another use it to
+reference predefined snippets. Both can help to avoid some duplication.
+
+This is a unique directive in that *import* can appear outside of a server block. In other words, it
+can appear at the top of a Corefile where an address would normally be.
+
+## Syntax
+
+~~~
+import PATTERN
+~~~
+
+*   **PATTERN** is the file, glob pattern (`*`) or snippet to include. Its contents will replace
+    this line, as if that file's contents appeared here to begin with.
+
+## Files
+
+You can use *import* to include a file or files. This file's location is relative to the
+Corefile's location. It is an error if a specific file cannot be found, but an empty glob pattern is
+not an error.
+
+## Snippets
+
+You can define snippets to be reused later in your Corefile by defining a block with a single-token
+label surrounded by parentheses:
+
+~~~ corefile
+(mysnippet) {
+	...
+}
+~~~
+
+Then you can invoke the snippet with *import*:
+
+~~~
+import mysnippet
+~~~
+
+## Examples
+
+Import a shared configuration:
+
+~~~
+. {
+   import config/common.conf
+}
+~~~
+
+Where `config/common.conf` contains:
+
+~~~
+prometheus
+errors
+log
+~~~
+
+This imports files found in the zones directory:
+
+~~~
+import ../zones/*
+~~~
+
+## Also See
+
+See corefile(5).