Improved image build instructions (#3580)

### What problem does this PR solve?

Improved arm64 image build instructions

### Type of change

- [x] Documentation Update
- [x] Refactoring

api/versions.py

@@ -13,26 +13,51 @@
 #  See the License for the specific language governing permissions and
 #  limitations under the License.
 #
+
+import os
 import subprocess
 
+RAGFLOW_VERSION_INFO = "unknown"
+
+
 def get_ragflow_version() -> str:
+    global RAGFLOW_VERSION_INFO
+    if RAGFLOW_VERSION_INFO != "unknown":
+        return RAGFLOW_VERSION_INFO
+    version_path = os.path.abspath(
+        os.path.join(
+            os.path.dirname(os.path.realpath(__file__)), os.pardir, "VERSION"
+        )
+    )
+    if os.path.exists(version_path):
+        with open(version_path, "r") as f:
+            RAGFLOW_VERSION_INFO = f.read().strip()
+    else:
+        RAGFLOW_VERSION_INFO = get_closest_tag_and_count()
+        LIGHTEN = int(os.environ.get("LIGHTEN", "0"))
+        RAGFLOW_VERSION_INFO += " slim" if LIGHTEN == 1 else " full"
     return RAGFLOW_VERSION_INFO
 
 
-RAGFLOW_VERSION_INFO = "dev"
-
-
 def get_closest_tag_and_count():
     try:
         # Get the current commit hash
-        commit_id = subprocess.check_output(['git', 'rev-parse', '--short', 'HEAD']).strip().decode('utf-8')
+        commit_id = (
+            subprocess.check_output(["git", "rev-parse", "--short", "HEAD"])
+            .strip()
+            .decode("utf-8")
+        )
         # Get the closest tag
-        closest_tag = subprocess.check_output(['git', 'describe', '--tags', '--abbrev=0']).strip().decode('utf-8')
-        # Get the commit hash of the closest tag
-        closest_tag_commit = subprocess.check_output(['git', 'rev-list', '-n', '1', closest_tag]).strip().decode(
-            'utf-8')
+        closest_tag = (
+            subprocess.check_output(["git", "describe", "--tags", "--abbrev=0"])
+            .strip()
+            .decode("utf-8")
+        )
         # Get the commit count since the closest tag
-        process = subprocess.Popen(['git', 'rev-list', '--count', f'{closest_tag}..HEAD'], stdout=subprocess.PIPE)
+        process = subprocess.Popen(
+            ["git", "rev-list", "--count", f"{closest_tag}..HEAD"],
+            stdout=subprocess.PIPE,
+        )
         commits_count, _ = process.communicate()
         commits_count = int(commits_count.strip())
 
@@ -41,8 +66,4 @@ def get_closest_tag_and_count():
         else:
             return f"{commit_id}({closest_tag}~{commits_count})"
     except Exception:
-        return 'unknown'
-
-
-if RAGFLOW_VERSION_INFO == 'dev':
-    RAGFLOW_VERSION_INFO = get_closest_tag_and_count()
+        return "unknown"