Misc: Add script for calculating MRVA totals

Use this script if you want to quickly calculate the totals of some
query across all the queries in a MRVA run.

For an example of such a query, see e.g.
`python/ql/src/Metrics/Internal/TypeAnnotations.ql`

The script expects the query to produce an output table of the form
```
| header0  | header1  | header2  | header3  | ...
|----------|----------|----------|----------|----
| message1 | value11  | value12  | value13  | ...
| message2 | value21  | value22  | value23  | ...
...
```
where all of the `values` are numbers. For each `(message, header)`
pair, it then calculates the total of all the values in that cell,
across all of the repos in the MRVA run.

To use the script, simply pass it the URL of the exported Gist of the
MRVA run. After calculating the totals, the script will then
(optionally, but by default) add the totals to the `_summary.md` file,
and push these changes to the Gist.

misc/scripts/calculate_mrva_totals.py

@@ -0,0 +1,131 @@
+import os
+import subprocess
+import tempfile
+import argparse
+from collections import defaultdict
+
+help_text = """
+To use this script, pass the URL of a GitHub Gist as an argument. The Gist should contain the
+exported MarkDown output of a MRVA run.
+
+The script expects the query to produce an output table of the form
+```
+| header0  | header1  | header2  | header3  | ...
+|----------|----------|----------|----------|----
+| message1 | value11  | value12  | value13  | ...
+| message2 | value21  | value22  | value23  | ...
+...
+```
+The script will calculate the totals for each message and header, and put a table containing these
+totals in the `_summary.md` file in the Gist. By default it will then commit and push these changes
+to the Gist (having first displayed a diff of the changes).
+"""
+
+first_header = ""
+
+def split_line(line):
+    return [item.strip() for item in line.strip('|').split('|')]
+
+def parse_markdown_table(stream):
+    global first_header
+    iterator = (line.strip() for line in stream)
+
+    # Skip irrelevant lines until we find the header line
+    for line in iterator:
+        if line.startswith('|'):
+            first_header, *headers = split_line(line)
+            break
+
+    # Skip the separator line
+    next(iterator)
+
+    data_dict = {}
+
+    # Process the remaining lines
+    for line in iterator:
+        if line.startswith('|'):
+            message, *values = [value.strip('`') for value in split_line(line)]
+            data_dict[message] = {
+                headers[i]: int(value) if value.isdigit() else value
+                for i, value in enumerate(values)
+            }
+
+    return data_dict
+
+def clone_gist(gist_url, repo_dir):
+    try:
+        subprocess.run(["gh", "gist", "clone", gist_url, repo_dir], check=True)
+    except subprocess.CalledProcessError:
+        print(f"Failed to clone the gist from {gist_url}")
+        subprocess.run(["rm", "-rf", repo_dir])
+        exit(1)
+
+def process_gist_files(repo_dir):
+    total_data = defaultdict(lambda: defaultdict(int))
+
+    for filename in os.listdir(repo_dir):
+        if filename.endswith(".md") and filename != "_summary.md":
+            with open(os.path.join(repo_dir, filename), "r") as file:
+                data_dict = parse_markdown_table(file)
+
+                for message, values in data_dict.items():
+                    for header, value in values.items():
+                        if isinstance(value, int):
+                            total_data[message][header] += value
+
+    return total_data
+
+def append_totals_to_summary(total_data, repo_dir):
+    global first_header
+    summary_path = os.path.join(repo_dir, "_summary.md")
+    with open(summary_path, "r") as summary_file:
+        content = summary_file.read()
+
+    totals_table = "\n\n### Totals\n\n"
+    headers = [first_header] + list(next(iter(total_data.values())).keys())
+    totals_table += "| " + " | ".join(headers) + " |\n"
+    totals_table += "| " + "|".join(["---"] + ["---:"] * (len(headers) - 1)) + " |\n"  # Right align all but the first column
+    for message, values in total_data.items():
+        row = [message] + [f"{values[header]:,}" for header in headers[1:]]
+        totals_table += "| " + " | ".join(row) + " |\n"
+
+    new_content = content.replace("### Summary", totals_table + "\n### Summary")
+
+    with open(summary_path, "w") as summary_file:
+        summary_file.write(new_content)
+
+def commit_and_push_changes(repo_dir):
+    subprocess.run(["git", "add", "_summary.md"], cwd=repo_dir, check=True)
+    subprocess.run(["git", "commit", "-m", "Update summary with totals"], cwd=repo_dir, check=True)
+    subprocess.run(["git", "push"], cwd=repo_dir, check=True)
+
+def show_git_diff(repo_dir):
+    subprocess.run(["git", "diff", "_summary.md"], cwd=repo_dir, check=True)
+
+if __name__ == "__main__":
+    parser = argparse.ArgumentParser(description="Calculate MRVA totals from a GitHub Gist", epilog=help_text, formatter_class=argparse.RawTextHelpFormatter)
+    parser.add_argument("gist_url", nargs='?', help="URL of the GitHub Gist")
+    parser.add_argument("--keep-dir", action="store_true", help="Keep the temporary directory")
+
+    args = parser.parse_args()
+
+    if not args.gist_url:
+        parser.print_help()
+        exit(1)
+
+    repo_dir = tempfile.mkdtemp(dir=".")
+    clone_gist(args.gist_url, repo_dir)
+
+    total_data = process_gist_files(repo_dir)
+
+    append_totals_to_summary(total_data, repo_dir)
+
+    show_git_diff(repo_dir)
+
+    if input("Do you want to push the changes to the gist? (Y/n): ").strip().lower() in ['y', '']:
+        commit_and_push_changes(repo_dir)
+
+    if args.keep_dir:
+        print(f"Temporary directory retained at: {repo_dir}")
+    else:
+        subprocess.run(["rm", "-rf", repo_dir])