gistfile1.js

var git = require('gulp-git');
var inject = require('inject-string');

// This successfully returns my git hash
gulp.task('hash', function() {
   git.revParse({args:'--short HEAD'}, function (err, hash) {
     return hash;
   });)
})

// How do I inject the return value of the hash task into the inject.append block?
gulp.task('html', function () {
  return gulp.src('app/index.html')
    .pipe(inject.append('append git hash here!'))
    .pipe(gulp.dest('dist'))
});