Add two scripts to check and get the current version of a crate

Author: zurawiki

scripts/get_current_version.sh

@@ -0,0 +1,18 @@
+#!/usr/bin/env bash
+
+# Script requirements:
+# - curl
+# - jq
+
+# Fail on first error, on undefined variables, and on failures in pipelines.
+set -euo pipefail
+
+# Go to the repo root directory.
+cd "$(git rev-parse --show-toplevel)"
+
+# The first argument should be the name of a crate.
+CRATE_NAME="$1"
+
+cargo metadata --format-version 1 | \
+    jq --arg crate_name "$CRATE_NAME" --exit-status -r \
+        '.packages[] | select(.name == $crate_name) | .version'

scripts/is_version_already_uploaded.sh

@@ -0,0 +1,44 @@
+#!/usr/bin/env bash
+
+# Script requirements:
+# - curl
+# - jq
+# - sort with `-V` flag, available in `coreutils-7`
+#   On macOS this may require `brew install coreutils`.
+
+# Fail on first error, on undefined variables, and on failures in pipelines.
+set -euo pipefail
+
+# Go to the repo root directory.
+cd "$(git rev-parse --show-toplevel)"
+
+# The first argument should be the name of a crate.
+CRATE_NAME="$1"
+
+CURRENT_VERSION="$(./scripts/get_current_version.sh "$CRATE_NAME")" || \
+    (echo >&2 "No crate named $CRATE_NAME found in workspace."; exit 1)
+echo >&2 "Crate $CRATE_NAME current version: $CURRENT_VERSION"
+
+# The leading whitespace is important! With it, we know that every version is both
+# preceded by and followed by whitespace. We use this fact to avoid matching
+# on substrings of versions.
+EXISTING_VERSIONS="
+$( \
+    curl 2>/dev/null "https://crates.io/api/v1/crates/$CRATE_NAME" | \
+    jq --exit-status -r .versions[].num \
+)"
+echo >&2 -e "Versions on crates.io:$EXISTING_VERSIONS\n"
+
+# Use version sort (sort -V) to get all versions in ascending order, then use grep to:
+# - grab the first line that matches the current version (--max-count=1)
+# - only match full lines (--line-regexp)
+OUTPUT="$( \
+    echo -e "$EXISTING_VERSIONS" | \
+    sort -V | \
+    grep --line-regexp --max-count=1 "$CURRENT_VERSION" || true
+)"
+
+if [[ "$OUTPUT" == "$CURRENT_VERSION" ]]; then
+    echo >&2 "The current version $CURRENT_VERSION is already on crates.io"
+    exit 7
+fi