Initial implementation

Wanted to see if this approach was doable.  It is very much so!

An alternative which is likely better: a small output processor for
`cram` which converts to TAP, so we can then run with `prove`.

README

@@ -0,0 +1,21 @@
+Usage: cramp [<OPTIONS> --] [<PATHS>]
+
+Cram, in parallel.
+
+If <OPTIONS> are given, they must be separated from test <PATHS> by "--".
+
+cramp options:
+  -jN, --jobs=N       number of tests to run in parallel
+  -h, --help          show this help message and exit
+  -V, --version       show version information and exit
+
+cram options:
+  -q, --quiet         don't print diffs
+  -v, --verbose       show filenames and test status
+  -d, --debug         write script output directly to the terminal
+  -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)
+  --xunit-file=PATH   path to write xUnit XML output

cram-log-merge

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+#!/usr/bin/env perl
+# Merge output from multiple invocations of Cram into one.
+use strict;
+use warnings;
+
+$|++; # unbuffer stdout
+
+my $ok   = 0;
+my $skip = 0;
+my $fail = 0;
+my $buf  = "";
+my $kept = "";
+
+while (<<>>) {
+    if (/^# Ran (\d+) tests, (\d+) skipped, (\d+) failed[.]/) {
+        # End of a Cram run; track counts and print output.
+        $ok   += $1;
+        $skip += $2;
+        $fail += $3;
+
+        chomp $buf if $buf =~ /^[.s!]+$/;
+        print $buf;
+        $buf = "";
+    }
+    elsif (/^# Kept temporary directory:/) {
+        # Hold --keep-tmpdir output till very end.
+        $kept .= $_;
+    }
+    else {
+        # Accumulate output from a Cram run
+        $buf .= $_;
+    }
+}
+
+die if $buf; # assert empty
+
+print "\n";
+print "# Ran $ok tests, $skip skipped, $fail failed.\n";
+print $kept if $kept;
+
+exit $fail;

cramp

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+#!/bin/bash
+set -euo pipefail
+
+main() {
+    # Separate options, if any, from paths.  If options are given, they must be
+    # delimited from paths with "--".
+    local -a cram_opts
+    local job_opt="--jobs=+0"
+
+    if [[ $# -eq 0 ]]; then
+        exit-with-help
+    fi
+    if [[ "${1:-}" == -* ]]; then
+        while [[ $# -gt 0 ]]; do
+            case "$1" in
+                --help|-h)
+                    exit-with-help;;
+
+                --version|-V)
+                    exit-with-version;;
+
+                --jobs=?*|-j?*)
+                    job_opt="$1"
+                    shift;;
+
+                --jobs|-j)
+                    job_opt="--jobs=$2"
+                    shift 2;;
+
+                --interactive|-i|--yes|-y|--no|-n)
+                    echo "cram's interactivity options (e.g. $1) are not supported under cramp" >&2
+                    exit 1;;
+
+                --)
+                    shift
+                    break;;
+
+                *)
+                    cram_opts+=("$1")
+                    shift;;
+            esac
+        done
+    fi
+
+      find "$@" -type f -name '*.t' -print0 \
+    | sort --zero-terminated \
+    | parallel --null --line-buffer --keep-order "$job_opt" -- cram "${cram_opts[@]}" \
+    | "$(dirname "$0")"/cram-log-merge
+}
+
+exit-with-help() {
+    cram --help | sed -Ee '
+        /^Usage: /c Usage: cramp [<OPTIONS> --] [<PATHS>]
+
+        /^Options:/ {
+            i Cram, in parallel.
+            i
+            i If <OPTIONS> are given, they must be separated from test <PATHS> by "--".
+            i 
+            i cramp options:
+            i \ \ -jN, --jobs=N       number of tests to run in parallel
+            i \ \ -h, --help          show this help message and exit
+            i \ \ -V, --version       show version information and exit
+            i 
+            c cram options:
+        }
+        /\s--(help|version)\s/d         # takeover help and version
+        /\s--(interactive|yes|no)\s/d   # no interactivity
+    '
+    exit
+}
+
+exit-with-version() {
+    echo "Cram, parallel (version 0)"
+    echo "Copyright 2024 Thomas Sibley <tom@zulutango.org>"
+    echo
+    cram --version
+    exit
+}
+
+main "$@"