Make :maps work on Windows and add :cmaps. (#1201)

* Make `:maps` work on Windows

This makes the `:maps` command from #1146 work on Windows.

This (as well as `:maps` itself) is based on @jackielli's work in #1146 and
#1152.

I intend to refactor the code in this or a separate PR, but I thought I'd
submit the critical and simple bit first.

* Add `:cmaps` command

After the naming scheme from #1146, it would seem weird to not have a :cmaps
command. This could help with issues like #876.

complete.go

@@ -14,6 +14,7 @@ var (
 		"map",
 		"maps",
 		"cmap",
+		"cmaps",
 		"cmd",
 		"quit",
 		"up",

doc.go

@@ -80,6 +80,7 @@ The following commands are provided by lf:
 	tag
 	tag-toggle               (default 't')
 	maps
+	cmaps
 
 The following command line commands are provided by lf:
 
@@ -605,8 +606,9 @@ Delete the next word in forward direction.
 Capitalize/uppercase/lowercase the current word and jump to the next word.
 
 	maps
+	cmaps
 
-List all key mappings.
+List all key mappings in normal mode or command-line editing mode.
 
 # Options
 

eval.go

@@ -2479,10 +2479,15 @@ func (e *callExpr) eval(app *app, args []string) {
 		app.ui.cmdAccLeft = acc
 		update(app)
 	case "maps":
-		cleanUp := app.runShell("$PAGER", nil, "$|")
+		cleanUp := app.runShell(envPager, nil, "$|")
 		io.Copy(app.cmdIn, listBinds(gOpts.keys))
 		app.cmdIn.Close()
 		cleanUp()
+	case "cmaps":
+		cleanUp := app.runShell(envPager, nil, "$|")
+		io.Copy(app.cmdIn, listBinds(gOpts.cmdkeys))
+		app.cmdIn.Close()
+		cleanUp()
 	default:
 		cmd, ok := gOpts.cmds[e.name]
 		if !ok {

lf.1

@@ -95,6 +95,7 @@ The following commands are provided by lf:
     tag
     tag-toggle               (default 't')
     maps
+    cmaps
 .EE
 .PP
 The following command line commands are provided by lf:
@@ -746,9 +747,10 @@ Capitalize/uppercase/lowercase the current word and jump to the next word.
 .PP
 .EX
     maps
+    cmaps
 .EE
 .PP
-List all key mappings.
+List all key mappings in normal mode or command-line editing mode.
 .SH OPTIONS
 This section shows information about options to customize the behavior. Character ':' is used as the separator for list options '[]int' and '[]string'.
 .PP