Add workflow to add DIRECTORY.md with... (TheAlgorithms#202)

* Add workflow to add `DIRECTORY.md` with list...

...of all files.

* Add `DIRECTORY.md` to trigger the workflow

* updating DIRECTORY.md

Co-authored-by: github-actions <${GITHUB_ACTOR}@users.noreply.github.com>

.github/workflows/directory_workflow.yml

@@ -0,0 +1,58 @@
+name: directory_md
+on: [push, pull_request]
+
+jobs:
+  MainSequence:
+    name: DIRECTORY.md
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v1 # v2 is broken for git diff
+      - uses: actions/setup-python@v2
+      - name: Setup Git Specs
+        run: |
+          git config --global user.name github-actions
+          git config --global user.email '${GITHUB_ACTOR}@users.noreply.github.com'
+          git remote set-url origin https://x-access-token:${{ secrets.GITHUB_TOKEN }}@github.com/$GITHUB_REPOSITORY
+      - name: Update DIRECTORY.md
+        shell: python
+        run: |
+            import os
+            from typing import Iterator
+            URL_BASE = "https://github.com/TheAlgorithms/C-Sharp/blob/master"
+            g_output = []
+            def good_filepaths(top_dir: str = ".") -> Iterator[str]:
+                fs_exts = tuple(".cs".split())
+                for dirpath, dirnames, filenames in os.walk(top_dir):
+                    dirnames[:] = [d for d in dirnames if d[0] not in "._"]
+                    for filename in filenames:
+                        if os.path.splitext(filename)[1].lower() in fs_exts:
+                            yield os.path.join(dirpath, filename).lstrip("./")
+            def md_prefix(i):
+                return f"{i * '  '}*" if i else "\n##"
+            def print_path(old_path: str, new_path: str) -> str:
+                global g_output
+                old_parts = old_path.split(os.sep)
+                for i, new_part in enumerate(new_path.split(os.sep)):
+                    if i + 1 > len(old_parts) or old_parts[i] != new_part:
+                        if new_part:
+                            g_output.append(f"{md_prefix(i)} {new_part.replace('_', ' ').title()}")
+                return new_path
+            def build_directory_md(top_dir: str = ".") -> str:
+                global g_output
+                old_path = ""
+                for filepath in sorted(good_filepaths(), key=str.lower):
+                    filepath, filename = os.path.split(filepath)
+                    if filepath != old_path:
+                        old_path = print_path(old_path, filepath)
+                    indent = (filepath.count(os.sep) + 1) if filepath else 0
+                    url = "/".join((URL_BASE, filepath, filename)).replace(" ", "%20")
+                    filename = os.path.splitext(filename.replace("_", " ").title())[0]
+                    g_output.append(f"{md_prefix(indent)} [{filename}]({url})")
+                return "# List of all files\n" + "\n".join(g_output)
+            with open("DIRECTORY.md", "w") as out_file:
+                out_file.write(build_directory_md(".") + "\n")
+      - name: Commit DIRECTORY.md
+        run: |
+         git commit -m "updating DIRECTORY.md" DIRECTORY.md ||  true
+         git diff DIRECTORY.md
+         git push --force origin HEAD:$GITHUB_REF || true