Add GitGrep plugin that makes the filename a link (#854)

* Add GitGrep plugin

* Fix lint

Author: drew-gross

src/plugins/GitGrep.tsx

@@ -0,0 +1,40 @@
+import * as React from "react";
+import {PluginManager} from "../PluginManager";
+import {Job} from "../shell/Job";
+import Link from "../utils/Link";
+import {join} from "path";
+import {colors} from "../views/css/colors";
+
+PluginManager.registerOutputDecorator({
+  decorate: (job: Job): React.ReactElement<any> => {
+    return <div style={{
+      padding: "10px",
+      lineHeight: "18px",
+    }}>{job.screenBuffer.toLines().map((line, index) => {
+      const match = line.match(/^(.*?):(\d+):(.*)$/);
+      if (match) {
+        const [, path, lineNum, rest] = match;
+        if (path && lineNum && rest) {
+          const absolutePath = join(job.environment.pwd, path);
+          return <div key={index.toString()}>
+            <Link absolutePath={absolutePath}>{path}</Link>
+            <span style={{color: colors.cyan}}>:</span>
+            {lineNum}
+            <span style={{color: colors.cyan}}>:</span>
+            <span style={{whiteSpace: "pre"}}>{rest}</span>
+          </div>;
+        }
+      }
+      return <div key={index.toString()}>{line}</div>;
+    })}</div>;
+  },
+
+  isApplicable: (job: Job): boolean => {
+    try {
+      const promptWords = job.prompt.expandedTokens.map(t => t.escapedValue);
+      return promptWords.length === 3 && promptWords[0] === "git" && promptWords[1] === "grep";
+    } catch (e) {
+      return false;
+    }
+  },
+});