Add readme and license

Author: nyancrimew

LICENSE

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+MIT License
+
+Copyright (c) 2020 Tillie Kottmann
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README.md

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+# goop
+
+Yet another tool to dump a git repository from a website. Code structure and console outputs heavily inspired by [arthaud/git-dumper](https://github.com/arthaud/git-dumper).
+
+## Usage
+```bash
+usage: goop [flags] url [dir]
+
+Flags:
+   -f, --force   overrides DIR if it already exists
+   -h, --help    help for goop
+```
+
+### Example
+```bash
+$ goop example.com
+```
+
+## Installation
+
+```bash
+go get -u github.com/deletescape/goop
+```
+
+## How does it work?
+
+The tool will first check if directory listing is available. If it is, then it will just recursively download the .git directory (what you would do with `wget`).
+
+If directory listing is not available, it will use several methods to find as many files as possible. Step by step, git-dumper will:
+* Fetch all common files (`.gitignore`, `.git/HEAD`, `.git/index`, etc.);
+* Find as many refs as possible (such as `refs/heads/master`, `refs/remotes/origin/HEAD`, etc.) by analyzing `.git/HEAD`, `.git/logs/HEAD`, `.git/config`, `.git/packed-refs` and so on;
+* Find as many objects (sha1) as possible by analyzing `.git/packed-refs`, `.git/index`, `.git/refs/*` and `.git/logs/*`;
+* Fetch all objects recursively, analyzing each commits to find their parents;
+* Run `git checkout .` to recover the current working tree