templates: add version func

Fixes #316

aerc.go

@@ -19,6 +19,7 @@ import (
 	"git.sr.ht/~sircmpwn/aerc/commands/terminal"
 	"git.sr.ht/~sircmpwn/aerc/config"
 	"git.sr.ht/~sircmpwn/aerc/lib"
+	"git.sr.ht/~sircmpwn/aerc/lib/templates"
 	libui "git.sr.ht/~sircmpwn/aerc/lib/ui"
 	"git.sr.ht/~sircmpwn/aerc/widgets"
 )
@@ -179,6 +180,9 @@ func main() {
 		as.OnMailto = aerc.Mailto
 	}
 
+	// set the aerc version so that we can use it in the template funcs
+	templates.SetVersion(Version)
+
 	close(initDone)
 
 	for !ui.ShouldExit() {

doc/aerc-templates.7.scd

@@ -125,6 +125,13 @@ aerc provides the following additional functions:
 	{{dateFormat .Date "Mon Jan 2 15:04:05 -0700 MST 2006"}}
 	```
 
+*version*
+	Returns the version of aerc, which can be useful for things like X-Mailer.
+
+	```
+	X-Mailer: aerc {{version}}
+	```
+
 *Function chaining*
 	All of the template functions can be chained together if needed.
 

lib/templates/template.go

@@ -16,6 +16,13 @@ import (
 	"github.com/mitchellh/go-homedir"
 )
 
+var version string
+
+//SetVersion initializes the aerc version displayed in template functions
+func SetVersion(v string) {
+	version = v
+}
+
 type TemplateData struct {
 	To      []*mail.Address
 	Cc      []*mail.Address
@@ -168,6 +175,7 @@ var templateFuncs = template.FuncMap{
 	"dateFormat": time.Time.Format,
 	"toLocal":    toLocal,
 	"exec":       cmd,
+	"version":    func() string { return version },
 }
 
 func findTemplate(templateName string, templateDirs []string) (string, error) {