Add removepref excmd

src/excmds.ts

@@ -491,13 +491,23 @@ export async function colourscheme(themename: string) {
  * Note that not all of the keys Firefox uses are suggested by Tridactyl.
  *
  * e.g.: `setpref general.warnOnAboutConfig false`
- * `setpref extensions.webextensions.restricterDomains ""`
  */
 //#background
 export function setpref(key: string, ...value: string[]) {
     return Native.writePref(key, value.join(" "))
 }
 
+/**
+ * Remove a setting from your user.js file.
+ *
+ * @param key The key that should be set. Must not be quoted. Must not contain spaces.
+ *
+ */
+//#background
+export function removepref(key: string) {
+    return Native.removePref(key)
+}
+
 /**
  * Like [[fixamo]] but quieter.
  *

src/lib/native.ts

@@ -758,6 +758,21 @@ export async function writePref(name: string, value: any) {
     }
 }
 
+/** Removes a preference from user.js */
+export async function removePref(name: string) {
+    const file = (await getProfileDir()) + "/user.js"
+    // No need to check the return code because read returns "" when failing to
+    // read a file
+    const text = (await read(file)).content
+    const prefPos = text.indexOf(`user_pref("${name}",`)
+    if (prefPos >= 0) {
+        let substr = text.substring(prefPos)
+        const prefEnd = substr.indexOf(";\n") + 1
+        substr = text.substring(prefPos, prefPos + prefEnd)
+        write(file, text.replace(substr, ``))
+    }
+}
+
 /** Obey Mozilla's orders https://github.com/tridactyl/tridactyl/issues/1800 */
 export async function unfixamo() {
     try {