_scripts: reduce toil syncing to cue-by-example

This adds a script to help reduce the toil of syncing content from this
repo to cue-labs/cue-by-example. Its results are visible in
cue-labs/cue-by-example#41.

The script is included here (and not in cue-labs/cue-by-example) because
its replacement is likely to be some preprocessor output mode, as
tracked in cue-lang/cue#3543.

Signed-off-by: Jonathan Matthews <[email protected]>
Change-Id: I58fc2af0d48f011745f936713ce48c417fffae38
Dispatch-Trailer: {"type":"trybot","CL":1203397,"patchset":3,"ref":"refs/changes/97/1203397/3","targetBranch":"master"}

_scripts/exportCueByExample.bash

@@ -0,0 +1,40 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# exportCueByExample.bash reads a single page from inside the hugo/ hierarchy,
+# performs a few simple transformations, and emits a form that's 80% ready to
+# be published at https://github.com/cue-labs/cue-by-example. This should be
+# superseded by a solution to https://cuelang.org/issue/3543.
+
+content="$1"
+
+# Line comments, in order (as they can't appear inline):
+#  awk: delete all content before the first Markdown H1
+#  sed:
+#  - any line with a text fenced code block is shell output
+#  - shell output needs not to have a dollar-space prefix
+#  - the opening of a code-tabs container isn't needed
+#  - a text code-tab element is a text file (NB this isn't always correct!)
+#  - a cue code-tab element is a CUE file
+#  - the closing of a code-tabs container marks the end of a fenced code block
+cat "$content" \
+| awk '/^# / { x=1 } ; x {print}' \
+| sed 's/^```text.*$/```sh/' \
+| sed 's/^\$ //' \
+| sed '/^{{< code-tabs >}}$/d' \
+| sed 's/^{{< code-tab .*language="txt".*$/```text/' \
+| sed 's/^{{< code-tab .*language="cue".*$/```cue/' \
+| sed 's@^{{< /code-tab >}}{{< /code-tabs >}}$@```@'
+
+cat <<EOC >&2
+
+ NBNBNBNBNBNBNBNBNBNBNBNBNBNBNBNBNBNBNBNBNBNBNBNBNBNBNBNBNBNBNBNBNBNBNBNB
+ The transformation of the source file $content
+ was successful, but MUST NOT be assumed to be complete. Make sure you audit
+ its output, paying close attention to:
+ - shell commands with a prefix marked as "Actual command in CUE-By-Example guide" (or similar)
+ - anything inside {{< ... >}} blocks, which don't mean anything in GitHub Markdown
+ - relative URLs inside [markdown](/links), as these won't resolve on GitHub
+ - fenced code blocks that originally had filetypes other than text might have been changed to "text"
+ NBNBNBNBNBNBNBNBNBNBNBNBNBNBNBNBNBNBNBNBNBNBNBNBNBNBNBNBNBNBNBNBNBNBNBNB
+EOC