build: make git fetch resilient on slow links

- improved_git now returns real git exit code; prefers HTTP/1.1
- fetch_from_repo retries fetch with depth=1 once and fails fast on fetch errors

scripts/general.sh

@@ -315,21 +315,27 @@ create_sources_list()
 #
 improved_git()
 {
-
-	local realgit=$(command -v git)
+	local realgit
+	realgit=$(command -v git)
 	local retries=3
 	local delay=10
 	local count=1
+	local last_status=0
+
+	# Prefer HTTP/1.1 for stability on flaky links.
+	# Also disable low-speed aborts (many environments have very low throughput).
 	while [ $count -lt $retries ]; do
-		$realgit "$@"
-		if [[ $? -eq 0 || -f .git/index.lock ]]; then
-			retries=0
+		$realgit -c http.version=HTTP/1.1 -c http.lowSpeedLimit=0 -c http.lowSpeedTime=0 "$@"
+		last_status=$?
+		if [[ $last_status -eq 0 || -f .git/index.lock ]]; then
 			break
 		fi
-	let count=$count+1
-	sleep $delay
+		let count=$count+1
+		sleep $delay
 	done
 
+	return $last_status
+
 }
 
 clean_up_git ()
@@ -630,14 +636,26 @@ fetch_from_repo()
 	fi # offline
 
 	if [[ $changed == true ]]; then
+		local fetch_depth=${GIT_FETCH_DEPTH:-200}
 
 		# remote was updated, fetch and check out updates
 		display_alert "Fetching updates"
 		case $ref_type in
-			branch) improved_git fetch --depth 200 origin "${ref_name}" ;;
-			tag) improved_git fetch --depth 200 origin tags/"${ref_name}" ;;
-			head) improved_git fetch --depth 200 origin HEAD ;;
+			branch) improved_git fetch --depth "${fetch_depth}" origin "${ref_name}" ;;
+			tag) improved_git fetch --depth "${fetch_depth}" origin tags/"${ref_name}" ;;
+			head) improved_git fetch --depth "${fetch_depth}" origin HEAD ;;
 		esac
+		local fetch_status=$?
+		if [[ $fetch_status -ne 0 && "${fetch_depth}" != "1" ]]; then
+			display_alert "Fetch failed; retrying with depth=1" "${workdir}" "wrn"
+			case $ref_type in
+				branch) improved_git fetch --depth 1 origin "${ref_name}" ;;
+				tag) improved_git fetch --depth 1 origin tags/"${ref_name}" ;;
+				head) improved_git fetch --depth 1 origin HEAD ;;
+			esac
+			fetch_status=$?
+		fi
+		[[ $fetch_status -ne 0 ]] && exit_with_error "Failed to fetch git sources" "${url} ${ref}"
 
 		# commit type needs support for older git servers that doesn't support fetching id directly
 		if [[ $ref_type == commit ]]; then