feat(auto update): add script to get tags from gitlab api

Signed-off-by: Aditya Alok <dev.aditya.alok@gmail.com>

scripts/updates/api/termux_gitlab_api_get_tag.sh

@@ -0,0 +1,114 @@
+# shellcheck shell=bash
+termux_gitlab_api_get_tag() {
+	if [[ -z "$1" ]]; then
+		termux_error_exit <<-EndOfUsage
+			Usage: ${FUNCNAME[0]} PKG_SRCURL [TAG_TYPE] [API_HOST]
+			Returns the latest tag of the given package.
+		EndOfUsage
+
+	fi
+	local PKG_SRCURL="$1"
+	local TAG_TYPE="${2:-}"
+	local API_HOST="${3:-gitlab.com}"
+
+	local project
+	project="$(echo "${PKG_SRCURL}" | cut -d'/' -f4-5)"
+	project="${project%.git}"
+
+	if [[ -z "${TAG_TYPE}" ]]; then # If not set, then decide on the basis of url.
+		if [[ "${PKG_SRCURL: -4}" == ".git" ]]; then
+			# Get newest tag.
+			TAG_TYPE="newest-tag"
+		else
+			# Get the latest release tag.
+			TAG_TYPE="latest-release-tag"
+		fi
+	fi
+
+	local jq_filter
+	local api_path
+
+	case "${TAG_TYPE}" in
+	latest-release-tag)
+		api_path="/releases"
+		jq_filter=".[0].tag_name"
+		;;
+	newest-tag)
+		api_path="/repository/tags"
+		jq_filter=".[0].name"
+		;;
+	*)
+		termux_error_exit <<-EndOfError
+			ERROR: Invalid TAG_TYPE: '${TAG_TYPE}'.
+			Allowed values: 'newest-tag', 'latest-release-tag'.
+		EndOfError
+		;;
+	esac
+
+	# Replace slash '/' with '%2F' in project name. It is required for Gitlab API.
+	local api_url="https://${API_HOST}/api/v4/projects/${project//\//%2F}${api_path}"
+	# Api can be accessed without authentication if the repository is publicly accessible.
+	# Default rate limit for gitlab.com is 300 requests per minute for unauthenticated users
+	# and non-protected paths which should be enough for most use cases.
+	# see: https://docs.gitlab.com/ee/user/gitlab_com/index.html#gitlabcom-specific-rate-limits
+	local response
+	response="$(
+		curl --silent --location --retry 10 --retry-delay 1 \
+			--write-out '|%{http_code}' \
+			"${api_url}"
+	)"
+
+	local http_code
+	http_code="${response##*|}"
+	# Why printf "%s\n"? Because echo interpolates control characters, which jq does not like.
+	response="$(printf "%s\n" "${response%|*}")"
+
+	local tag_name
+	if [[ "${http_code}" == "200" ]]; then
+		if jq --exit-status --raw-output "${jq_filter}" <<<"${response}" >/dev/null; then
+			tag_name="$(jq --exit-status --raw-output "${jq_filter}" <<<"${response}")"
+		else
+			termux_error_exit "ERROR: Failed to parse tag name from: '${response}'"
+		fi
+	elif [[ "${http_code}" == "404" ]]; then
+		if jq --exit-status "has(\"message\") and .message == \"Not Found\"" <<<"${response}"; then
+			termux_error_exit <<-EndOfError
+				ERROR: No '${TAG_TYPE}' found. (${api_url})
+				Try using '$(
+					if [ ${TAG_TYPE} = "newest-tag" ]; then
+						echo "latest-release-tag"
+					else
+						echo "newest-tag"
+					fi
+				)'.
+			EndOfError
+		else
+			termux_error_exit <<-EndOfError
+				ERROR: Failed to get '${TAG_TYPE}' (${api_url}).
+				Response:
+				${response}
+			EndOfError
+		fi
+	elif [[ "${http_code}" == "304" ]]; then
+		return 2 # Up-to-date.
+	else
+		termux_error_exit <<-EndOfError
+			ERROR: Failed to get '${TAG_TYPE}' (${api_url}).
+			HTTP code: ${http_code}
+			Response:
+			${response}
+		EndOfError
+	fi
+
+	# If program control reached here and still no tag_name, then something is not right.
+	if [[ -z "${tag_name:-}" ]] || [[ "${tag_name}" == "null" ]]; then
+		termux_error_exit <<-EndOfError
+			ERROR: JQ could not find '${TAG_TYPE}' (${api_url}).
+			Response:
+			${response}
+			Please report this as bug.
+		EndOfError
+	fi
+
+	echo "${tag_name#v}" # Strip leading 'v'.
+}