feat(CONTRIB) +demo script to proc changes with cmd >

adapted  from lint demo,  but commands output can be a different file.

Signed-off-by: Kostis Anagnostopoulos <[email protected]>

contrib/filter-repo-demos/README.md

@@ -17,6 +17,7 @@ clean-ignore         |Delete files from history which match current gitignore ru
 filter-lamely (or filter‑branch‑ish) |A nearly bug compatible re-implementation of filter-branch (the git testsuite passes using it instead of filter-branch), with some performance tricks to make it several times faster (though it's still glacially slow compared to filter-repo).
 bfg-ish              |A re-implementation of most of BFG Repo Cleaner, with new features and bug fixes.
 convert-svnexternals |Insert Git submodules according to SVN externals.
+proc-history         | Run shell command on each file in history and add or replace the file with cmd's output.                                                                                                                               
 
 ## Purpose
 

contrib/filter-repo-demos/proc-history.py

@@ -0,0 +1,307 @@
+#!/usr/bin/env python3
+
+"""
+Run shell command on each file in history and add or replace the file with cmd's output.
+
+It also rewrites commit hashes in commit messages to
+refer to the new commits with the rewritten files.
+
+Run <prog> --help for more details.
+   <prog> py:percent --arg whatever --another-arg
+
+Based on https://github.com/newren/git-filter-repo/blob/main/contrib/filter-repo-demos/lint-history
+
+NOTE: Several people have taken and modified this script for a variety
+of special cases (linting python files, linting jupyter notebooks, just
+linting java files, etc.) and posted their modifications at
+  https://github.com/newren/git-filter-repo/issues/45
+Feel free to take a look and adopt some of their ideas.  Most of these
+modifications are probably strictly unnecessary since you could just make
+a lint-script that takes the filename, checks that it matches what you
+want, and then calls the real linter.  But I guess folks don't like making
+an intermediate script.  So I eventually added the --relevant flag for
+picking out certain files providing yet another way to handle it.
+
+Please see the
+  ***** API BACKWARD COMPATIBILITY CAVEAT *****
+near the top of git-filter-repo.
+"""
+
+# Technically, if you are only running on all non-binary files and don't care
+# about filenames, then this program could be replaced by a "one-liner"; e.g.
+#    git filter-repo --force --blob-callback '
+#      if not b"\0" in blob.data[0:8192]:
+#        filename = '.git/info/tmpfile'
+#        with open(filename, "wb") as f:
+#          f.write(blob.data)
+#        subprocess.check_call(["lint_program", "--some", "arg", filename])
+#        with open(filename, "rb") as f:
+#          blob.data = f.read()
+#        os.remove(filename)
+#      '
+# but let's do it as a full-fledged program that imports git_filter_repo
+# and show how to also do it with filename handling...
+
+import argparse
+import os
+from pathlib import Path, PurePath
+from typing import List
+import subprocess
+import tempfile
+import textwrap
+
+try:
+    import git_filter_repo as fr
+except ImportError:
+    raise SystemExit(
+        "Error: Couldn't find git_filter_repo.py. "
+        "\n  Did you symlink your in-PATH `git-filter-repo` --> `git_filter_repo.py` "
+        "or did you forget to put the latter in your PYTHONPATH?"
+    )
+
+example_text = """CALLBACKS
+
+    When you pass --relevant 'BODY', the following style of function
+    will be compiled and called:
+
+        def is_relevant(fpath: pathlib.PurePath) -> bool:
+            BODY
+
+    where `fpath` is a pathlib.PurePath instance with the full relative path
+    from the toplevel of the repository.
+
+    Respectively the --outfpath 'BODY', the following style of function is formed:
+
+        def make_out_fpath(fpath: pathlib.Path) -> pathlib.Path:
+            BODY
+
+EXAMPLES
+
+    To only process files with a ".txt" extension you would run
+
+        %(prog)s --relevant 'return fpath.suffix.lower() == ".txt"' ...
+
+    To convert all notebooks in history to py:percent (the default)
+    with the `jupyext` comandv (notice the "--" pseudo-argumernt is needed
+    for considering the `--to <format>` option as part of the `command`):
+
+        %(prog)s \\
+            --relevant 'return fpath.suffix.lower() == ".ipynb"'  \\
+            --outfpath 'return fpath.with_suffix(".py")' \\
+            --drop-src \\
+            -- \\
+            jupytext --to 'py:percent'
+
+    To maintain a CONTENTS.txt file with all file headers on each commit
+    (in bash, and not the best use this tool):
+
+    $ file-header() {
+        echo "- $1:"
+        head -n3 $1 |  sed 's/^/    /'
+        echo
+    }
+    $ export -f file-header collect-
+    $ %(prog)s \\
+        --relevant 'return fpath.suffix.lower() == ".ipynb"'  \\
+        --outfpath 'return fpath.with_suffix(".py")' \\
+        --drop-src \\
+        -- \\
+        jupytext --to 'py:percent'
+
+INTERNALS
+
+    Processing of files in history is done by writting the "relevant" files
+    into a temporary directory before running the `command` which should produce
+    the new file specified by the --outpath; the location of this temporary directory
+    can be controlled via the TMPDIR environment variable as per
+    https://docs.python.org/3/library/tempfile.html#tempfile.mkdtemp.
+    """
+
+parser = argparse.ArgumentParser(
+    description="Run a program over files in history to convert them or append more",
+    epilog=example_text,
+    formatter_class=argparse.RawDescriptionHelpFormatter,
+)
+
+parser.add_argument(
+    "--relevant",
+    metavar="FUNCTION_BODY",
+    help=(
+        """
+    Python code returning truthy when `command` should run for `fpath`
+    (given as a `pathlib.PurePath` instance).\
+    If not given, all files are relevant [%(default)s].
+    See CALLBACKS, below.
+    """
+    ),
+    default="return True",
+)
+parser.add_argument(
+    "--outpath",
+    metavar="FUNCTION_BODY",
+    help="""
+    Python code returning the output filepath when `command` runs on a source `fpath`
+    (given as a `pathlib.Path` instance).
+    If not given, same as source assumed [%(default)s].
+    Note that the command runs in a temporary dir, so leave its parent paths as is.
+    See CALLBACKS, below.
+    """,
+    default="return fpath",
+)
+parser.add_argument(
+    "--drop-src",
+    action="store_true",
+    help=(
+        "Replace the relevant file with the --outpath from `command` "
+        "(by default both source & destination paths are kept in history).  "
+        "Ignored if `outpath` identical to source."
+    ),
+)
+parser.add_argument(
+    "--exec-shell",
+    action="store_true",
+    help="Whether to execute the command in a shell (eg. to inherit functions).",
+)
+parser.add_argument(
+    "--refs",
+    nargs="+",
+    help=(
+        "Limit history rewriting to the specified refs. "
+        "Implies --partial of git-filter-repo (and all its "
+        "implications)."
+    ),
+)
+parser.add_argument(
+    "--force",
+    "-f",
+    action="store_true",
+    help=" Rewrite history even if the current repo does not look like a fresh clone.",
+)
+parser.add_argument(
+    "command",
+    nargs="+",
+    help="""
+        The command to process each relevant file and produce `outpath` 
+        *without* its filename at the end.
+        See INTERNALS, below.
+    """,
+)
+cli_args = parser.parse_args()
+if not cli_args.command:
+    raise SystemExit("Error: Need to specify a file-processing command")
+
+utf8 = "utf-8"
+blobs_handled = {}
+cat_file_process = None
+
+
+def process_file(change: fr.FileChange) -> List[fr.FileChange]:
+    # Get the old blob contents
+    cat_file_process.stdin.write(change.blob_id + b"\n")
+    cat_file_process.stdin.flush()
+    objhash, objtype, objsize = cat_file_process.stdout.readline().split()
+    contents_plus_newline = cat_file_process.stdout.read(int(objsize) + 1)
+
+    src = PurePath(change.filename.decode(utf8))
+
+    try:
+        # Write it out to a file with the same basename
+        tmp_src = tmpdir / src.name
+        with open(tmp_src, "wb") as f:
+            f.write(contents_plus_newline[:-1])
+
+        # Execute the command
+        cmd_args = [*cli_args.command, str(tmp_src)]
+        subprocess.check_call(cmd_args, shell=cli_args.exec_shell)
+
+        # Validate output indeed created..
+        tmp_out = make_out_fpath(tmp_src)
+        try:
+            if not tmp_out.exists():
+                raise SystemExit(
+                    f"Error: command({' '.join(cmd_args)!r}) should have created file: {tmp_out}"
+                )
+
+            # Get the new contents
+            with open(tmp_out, "rb") as f:
+                blob = fr.Blob(f.read())
+
+            # Remove tempfiles
+        finally:
+            tmp_out.unlink(missing_ok=True)
+    finally:
+        tmp_src.unlink()
+
+    # Insert the new file into the filter's stream, and remove the tempfile
+    filter.insert(blob)
+
+    new_changes = []
+
+    if src.name == tmp_out.name:
+        # Record processing to update blob-references in this and future changes.
+        blobs_handled[change.blob_id] = change.blob_id = blob.id
+    else:
+        new_filename = str(src.with_name(tmp_out.name)).encode(utf8)
+        change_type = b"M"  # no need for b'A' ever
+        if cli_args.drop_src:
+            # Dress current change as the out-file and delete old
+            # and record processing to update blob-references.
+            new_changes.append(fr.FileChange(b"D", change.filename))
+            blobs_handled[change.blob_id] = change.blob_id = blob.id
+            change.filename = new_filename
+            change.type = change_type
+        else:
+            # Add/modify new out-file and keep old (so no blob-refs updates)
+            new_changes.append(
+                fr.FileChange(change_type, new_filename, blob.id, change.mode)
+            )
+
+    return new_changes
+
+
+def process_file_changes(commit: fr.Commit, metadata):
+    new_changes = []
+    file_changes: list[fr.FileChange] = commit.file_changes
+    for change in file_changes:
+        if change.blob_id in blobs_handled:
+            change.blob_id = blobs_handled[change.blob_id]
+        elif change.type == b"D" or not is_relevant(
+            PurePath(change.filename.decode(utf8))
+        ):
+            continue
+        else:
+            new_changes.extend(process_file(change))
+
+    file_changes.extend(new_changes)
+
+
+body = textwrap.indent(cli_args.relevant, "  ")
+exec(
+    f"def is_relevant(fpath):\n{body}",
+    globals(),
+)
+body = textwrap.indent(cli_args.outpath, "  ")
+exec(
+    f"def make_out_fpath(fpath):\n{body}",
+    globals(),
+)
+
+
+filter_args = []
+if cli_args.refs:
+    filter_args = ["--replace-refs", "update-no-add", "--refs", *cli_args.refs]
+fr_args = fr.FilteringOptions.parse_args(filter_args, error_on_empty=False)
+if cli_args.force:
+    fr_args.force = True
+tmpdir = Path(tempfile.mkdtemp())
+cat_file_process = subprocess.Popen(
+    ["git", "cat-file", "--batch"], stdin=subprocess.PIPE, stdout=subprocess.PIPE
+)
+
+filter = fr.RepoFilter(fr_args, commit_callback=process_file_changes)
+filter.run()
+
+cat_file_process.stdin.close()
+cat_file_process.wait()
+
+tmpdir.rmdir()