Add ZSH support

Author: 9ary

Cargo.lock

@@ -1,6 +1,7 @@
 [package]
 name = "gitprompt-rs"
-version = "0.1.2"
+version = "0.2.0"
 authors = ["Dan Elkouby <streetwalkermc@gmail.com>"]
 
 [dependencies]
+"lazy_static" = "1.1.0"

Cargo.toml

@@ -6,18 +6,9 @@ A very simple Git prompt written in Rust
 
 Just add `$(gitprompt-rs)` to your shell prompt.
 
-If you're using ZSH, add `setopt promptsubst` to your zshrc, set the `PROMPT`
-variable with single quotes `'`, and use the following function to wrap the
-output:
-```shell
-function pr_git() {
-    # Wrap SGR sequences with %{ and %} to avoid confusing zsh's length calculation
-    gitprompt-rs | perl -p -e 's/(\[.+?m)/%{\1%}/g'
-}
-```
-This isn't built into the program for compatibility with other shells while
-keeping things as simple as possible, and the overhead of calling Perl isn't
-that big anyway.
+If you're using ZSH, you will want to use `$(gitprompt-rs zsh)` in order to
+insert the appropriate escapes in the output, otherwise, it will miscalculate
+the length of your prompt and go crazy.
 
 The prompt looks like this: `(master↑4↓7|+2~3-5x6•8)`. The information on
 display is as follows:

README.md

@@ -2,9 +2,13 @@
 // License, v. 2.0. If a copy of the MPL was not distributed with this
 // file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
+use std::env;
 use std::error::Error;
 use std::process;
 
+#[macro_use]
+extern crate lazy_static;
+
 struct GitStatus {
     branch: Option<String>,
     ahead: i64,
@@ -17,20 +21,45 @@ struct GitStatus {
     untracked: i64,
 }
 
+lazy_static! {
+    static ref ZSH_ESCAPE: bool = {
+        match env::args().nth(1) {
+            Some(arg) => arg == "zsh",
+            _ => false,
+        }
+    };
+}
+
+fn zsh_escape_start() {
+    if *ZSH_ESCAPE {
+        print!("%{{");
+    }
+}
+
+fn zsh_escape_end() {
+    if *ZSH_ESCAPE {
+        print!("%}}");
+    }
+}
+
 fn color(c: i32) {
+    zsh_escape_start();
     if c >= 0 {
         print!("\x1b[38;5;{}m", c);
     } else {
         print!("\x1b[39m");
     }
+    zsh_escape_end();
 }
 
 fn bold(b: bool) {
+    zsh_escape_start();
     if b {
         print!("\x1b[1m");
     } else {
         print!("\x1b[22m");
     }
+    zsh_escape_end();
 }
 
 fn parse_porcelain2(data: String) -> Option<GitStatus> {