templates: allow inline user styles

Allow custom user-defined styles in a styleset. The styles can take any
name, and must be under the [user] ini section. All attributes apply to
user defined styles.

Example:

	[user]
	red.fg=red
	red.bold=true

Add a .Style function which accepts the name of a user-defined style and
applies it to the string.

	{{.Style "red" "foo"}}

Signed-off-by: Tim Culverhouse <tim@timculverhouse.com>
Acked-by: Robin Jarry <robin@jarry.cc>

1 files changed, 12 insertions, 0 deletions

diff --git a/doc/aerc-stylesets.7.scd b/doc/aerc-stylesets.7.scd
index eaedb4cb..c633dcef 100644
--- a/doc/aerc-stylesets.7.scd
+++ b/doc/aerc-stylesets.7.scd
@@ -166,6 +166,18 @@ declared under a *[viewer]* section of the styleset file.
 |  *quote_x*
 :  Above fourth level quoted text.
 
+User defined styles can be used to style arbitrary strings in go-templates (see
+_.Style_ in *aerc-templates*(7)). User styles must be defined in the _[user]_
+ini section. Styles can be referenced by their name (e.g. _red.fg_ is named
+"red").
+
+Example:
+
+```
+[user]
+red.fg=red
+```
+
 ## FNMATCH STYLE WILDCARD MATCHING
 
 The styleset configuration can be made simpler by using the fnmatch