Initial implementation

TAP is so good.  Converting Cram's output to TAP makes it possible to
use `prove`, e.g.

    prove --exec=cram-tap tests/

and being able to use `prove` (or any other TAP runner/harness!) opens
up features like parallelization with smart start-slowest-first
behaviour, e.g.

    prove --exec=cram-tap -j9 --state=slow,save tests/

This produces TAP by converting Cram's xUnit output.  It would be better
(and I suspect very much not difficult) to add TAP output directly to
Cram.  I'll leave that for another time.

README

@@ -0,0 +1,14 @@
+Usage: cram-tap [OPTIONS] TESTS...
+
+A TAP-emitting Cram.
+
+cram-tap options:
+  -h, --help          show this help message and exit
+  -V, --version       show version information and exit
+
+cram options:
+  -E, --preserve-env  don't reset common environment variables
+  --keep-tmpdir       keep temporary directories
+  --shell=PATH        shell to use for running tests (default: /bin/sh)
+  --shell-opts=OPTS   arguments to invoke shell with
+  --indent=NUM        number of spaces to use for indentation (default: 2)

cram-tap

@@ -0,0 +1,62 @@
+#!/bin/bash
+set -euo pipefail
+
+main() {
+    if [[ $# -eq 0 ]]; then
+        exit-with-help
+    fi
+
+    # Validate arguments
+    for arg; do
+        case "$arg" in
+            --help|-h)
+                exit-with-help;;
+
+            --version|-V)
+                exit-with-version;;
+
+            --interactive|-i|--yes|-y|--no|-n)
+                echo "cram's interactivity options (e.g. $1) are not supported under cram-tap" >&2
+                exit 1;;
+
+            --quiet|-q|--verbose|-v|--debug|-d|--xunit-file)
+                echo "cram's output control options (e.g. $1) are not supported under cram-tap" >&2
+                exit 1;;
+        esac
+    done
+
+    # XXX TODO: Maybe unmask cram's exit status depending on if it matches
+    # failed test count?
+    #   -trs, 13 Nov 2024
+    cram "$@" --xunit-file=>("$(dirname "$0")"/cram-xunit-to-tap) >/dev/null || true
+}
+
+exit-with-help() {
+    cram --help | sed -Ee '
+        1s/^Usage: cram /Usage: cram-tap /
+
+        /^Options:/ {
+            i A TAP-emitting Cram.
+            i
+            i cram-tap options:
+            i \ \ -h, --help          show this help message and exit
+            i \ \ -V, --version       show version information and exit
+            i 
+            c cram options:
+        }
+        /\s--(help|version)\s/d                         # takeover help and version
+        /\s--(quiet|verbose|debug|xunit-file=PATH)\s/d  # no output control
+        /\s--(interactive|yes|no)\s/d                   # no interactivity
+    '
+    exit
+}
+
+exit-with-version() {
+    echo "cram-tap (version 0)"
+    echo "Copyright 2024 Thomas Sibley <[email protected]>"
+    echo
+    cram --version
+    exit
+}
+
+main "$@"

cram-xunit-to-tap

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+#!/usr/bin/env python3
+import xml.etree.ElementTree as ET
+from sys import stdin, stdout
+from textwrap import indent
+
+doc = ET.parse(stdin)
+suite = doc.getroot()
+
+assert suite.tag == "testsuite" and suite.get("name") == "cram"
+
+count = int(suite.get("tests", 0))
+
+print("TAP version 13")
+print(f"1..{count:d}")
+
+escape = lambda text: text.replace("\\", "\\\\").replace("#", "\\#")
+comment = lambda text: indent(text, "# ", lambda line: True)
+
+for i, test in enumerate(suite.findall("./testcase"), 1):
+    if file := test.get("classname"):
+        description = "- " + escape(file)
+    else:
+        description = ""
+
+    if (failure := test.find("failure")) is not None:
+        print("not ok", i, description)
+        print(comment(failure.text))
+
+    elif test.find("skipped") is not None:
+        # Skipped tests in TAP may be ok or not ok, but Cram doesn't tell us.
+        print("ok", i, description, "# SKIP")
+
+    else:
+        assert len(test) == 0
+        print("ok", i, description)