Add simple Weblate screenshot uploader tool

Uploads all page layout test results via Weblate's API.

Makefile

@@ -310,6 +310,10 @@ update-user-guides:  ## Run the page layout tests to regenerate screenshots.
 	@$(DEVSHELL) $(SDBIN)/update-user-guides
 	@echo
 
+.PHONY: upload-screenshots
+upload-screenshots: ## Upload all English language screenshots to Weblate.
+	$(SDBIN)/upload-screenshots
+	@echo
 
 ###########
 #

securedrop/bin/upload-screenshots

@@ -0,0 +1,58 @@
+#!/bin/bash
+#
+# A maintenance script for uploading all screenshots generated by the page
+# layout tests to Weblate, to provide context for translators. Only the
+# English language screenshots are uploaded.
+#
+# Currently this script does not perform checks for existing screenshots;
+# it just blindly uploads the entire set of screenshots, which then have
+# to be manually associated with the correct strings.
+
+# Standard shell safety settings
+set -e
+set -u
+set -o pipefail
+
+if [ -z "${WEBLATE_BASE_URL:-}" ]; then
+   WEBLATE_BASE_URL="https://weblate.securedrop.org/"
+fi
+
+if [ -z "${WEBLATE_API_KEY:-}" ]; then
+   echo "WEBLATE_API_KEY environment variable is not set. This script requires"
+   echo "an API key to be configured to perform file uploads. You can obtain"
+   echo "one via this link: ${WEBLATE_BASE_URL}accounts/profile/#api"
+   exit 1
+fi
+
+BASEDIR=$(dirname "$0")
+FILES="$BASEDIR/../tests/pageslayout/screenshots/en_US/*.png"
+
+for file in $FILES
+do
+  if [ ! -f "$file" ]; then
+    echo "Page layout test results not found. Run this command from the SecureDrop"
+    echo "base directory to generate the English language screenshots. This will"
+    echo "take several minutes."
+    echo
+    echo "LOCALES=en_US make translation-test"
+    exit 1
+  fi
+  BASENAME=$(basename "$file")
+  # Generate more readable titles for use within Weblate.
+  # Example conversion: "source-session_timeout.png" -> "source: session timeout"
+  TITLE=$(echo "${BASENAME}" | sed -e "s/\.png//" | sed -e "s/-/: /g" | sed -e "s/_/ /g")
+
+  echo "Uploading '${BASENAME}' to Weblate."
+  echo "API result:"
+  curl -w "\nHTTP code: %{http_code}\n" \
+    -H "Authorization: Token ${WEBLATE_API_KEY}" \
+    -F "image=@${file}" \
+    -F "name=${TITLE}" \
+    -F "project_slug=securedrop" \
+    -F "component_slug=securedrop" \
+    "${WEBLATE_BASE_URL}api/screenshots/"
+  echo
+  echo
+done
+
+echo "Upload complete."