Add a script to check differences between translated and English version (#14731)

This script will query all the changes that happen to a reference document (in English) since the last time a given translation was merged (For instance in French).
This could help all the translation team to keep up with the changes that happened inside the reference document.

scripts/upstream_changes.py

@@ -0,0 +1,78 @@
+#!/usr/bin/env python
+
+import re
+from subprocess import check_output
+
+import click
+
+
+def last_commit(path, git):
+    """
+    Find the hash of the last commit that touched a file.
+    """
+    cmd = [git, "log", "-n", "1", "--pretty=format:%H", "--", path]
+    try:
+        return check_output(cmd)
+    except Exception as exc:
+        raise exc
+
+
+def diff(reference_commit_hash, translation_commit_hash, reference_path, git):
+    """
+    Returns the diff between two hashes on a specific file
+    """
+    cmd = [git, "diff",
+           "%s...%s" % (translation_commit_hash, reference_commit_hash),
+           "--",
+           reference_path]
+    try:
+        return check_output(cmd)
+    except Exception as exc:
+        raise exc
+
+
+def find_full_path(path, git):
+    cmd = [git, "ls-tree",
+           "--name-only", "--full-name", "HEAD",
+           path]
+    try:
+        return check_output(cmd).strip()
+    except Exception as exc:
+        raise exc
+
+
+def find_reference(path, git):
+    abs_path = find_full_path(path, git=git)
+    return re.sub('content/(\w{2})/', 'content/en/', abs_path)
+
+
+@click.command()
+@click.argument("path")
+@click.option("--reference", "reference",
+              help="Specify the reference version of the file. Default to the English one.",
+              default=None)
+@click.option("--git-path",
+              "git",
+              help="Specify git path",
+              default="git")
+def main(path, reference, git):
+    """
+    Find what changes occurred between two versions
+
+    ex:
+    ./upstream_changes.py content/fr/_index.html
+    """
+    if reference is None:
+        reference = find_reference(path, git=git)
+    reference_commit_hash = last_commit(path=reference, git=git)
+    translation_commit_hash = last_commit(path=path, git=git)
+
+    print(diff(
+        reference_commit_hash=reference_commit_hash,
+        translation_commit_hash=translation_commit_hash,
+        reference_path=reference,
+        git=git
+    ))
+
+if __name__ == '__main__':
+    main()