Add red-hat-openshift script (#119)

The script only get versions 4.x and above, see script comments for more informations.

Note that the code related to git has been extracted to a common script so that it can be reused for the Debian script.

src/common/git.py

@@ -0,0 +1,76 @@
+from subprocess import call, Popen, PIPE, DEVNULL
+from typing import Union, List
+from pathlib import Path
+from hashlib import sha1
+
+class Git:
+    """
+    Git cli wrapper
+    used by debian.py and red-hat-openshift.py
+    """
+
+    def __init__(self, url: str):
+        self.url: str = url
+        self.repo_dir: Path = Path(
+            f"~/.cache/git/{sha1(self.url.encode()).hexdigest()}"
+        ).expanduser()
+
+    def _run(self, cmd: str, return_output: bool = False) -> Union[bool, list]:
+        """
+        Run git command and return True on success or False on failure.
+        Optionaly returns command result instead.
+        """
+        git_opts = f"--git-dir={self.repo_dir}/.git --work-tree={self.repo_dir}"
+
+        if return_output:
+            child = Popen(
+                f"git {git_opts} {cmd}",
+                shell=True,
+                stdout=PIPE,
+            )
+            return child.communicate()[0].decode("utf-8").split("\n")
+
+        return call(f"git {git_opts} {cmd}",
+                    shell=True,
+                    stdout=DEVNULL,
+                    stderr=DEVNULL) == 0
+
+    def setup(self):
+        """
+        Creates the repository path and runs:
+        git init
+        git remote add origin $url
+        """
+        self.repo_dir.mkdir(parents=True, exist_ok=True)
+        if not Path(f"{self.repo_dir}/.git").exists():
+            self._run("init")
+            self._run(f"remote add origin {self.url}")
+
+    def list_branches(self, pattern: str):
+        """
+        Uses ls-remote to fetch the branch names
+        `pattern` uses fnmatch style globbing
+        """
+        raw = self._run(
+            # only list v4+ branches because the format in v3 is different
+            f"ls-remote origin '{pattern}'",
+            return_output=True,
+        )
+
+        # this checks keeps the linter quiet, because _run returns a bool OR list
+        # please dont remove
+        if isinstance(raw, bool):
+            return []
+
+        return [line.split("\t")[1][11:] for line in raw if "\t" in line]
+
+    def checkout(self, branch: str, file_list: List[str] = []):
+        """
+        Checks out a branch
+        If `file_list` is given, sparse-checkout is used to save bandwith
+        and only download the given files
+        """
+        if file_list:
+            self._run(f"sparse-checkout set {' '.join(file_list)}")
+        self._run(f"fetch --filter=blob:none --depth 1 origin {branch}")
+        self._run(f"checkout {branch}")