Update fetch option documentation

PiperOrigin-RevId: 601517575
Change-Id: I29e42582b6a6fc06506473a53d85370bd0288c19

site/en/external/overview.md

@@ -98,6 +98,18 @@ Normally, Bazel only fetches a repo when it needs something from the repo,
 and the repo hasn't already been fetched. If the repo has already been fetched
 before, Bazel only re-fetches it if its definition has changed.
 
+The `fetch` command can be used to initiate a pre-fetch for a repository,
+target, or all necessary repositories to perform any build. This capability
+enables offline builds using the `--nofetch` option.
+
+The `--fetch` option serves to manage network access. Its default value is true.
+However, when set to false (`--nofetch`), the command will utilize any cached
+version of the dependency, and if none exists, the command will result in
+failure.
+
+See [fetch options](/reference/command-line-reference#fetch-options) for more
+information about controlling fetch.
+
 ### Directory layout {:#directory-layout}
 
 After being fetched, the repo can be found in the subdirectory `external` in the

src/main/java/com/google/devtools/build/lib/pkgcache/PackageOptions.java

@@ -168,12 +168,14 @@ public ParallelismConverter() throws OptionsParsingException {
   public int maxDirectoriesToEagerlyVisitInGlobbing;
 
   @Option(
-    name = "fetch",
-    defaultValue = "true",
-    documentationCategory = OptionDocumentationCategory.UNDOCUMENTED,
-    effectTags = {OptionEffectTag.UNKNOWN},
-    help = "Allows the command to fetch external dependencies"
-  )
+      name = "fetch",
+      defaultValue = "true",
+      documentationCategory = OptionDocumentationCategory.UNCATEGORIZED,
+      effectTags = {OptionEffectTag.UNKNOWN},
+      help =
+          "Allows the command to fetch external dependencies. If set to false, the command will"
+              + " utilize any cached version of the dependency, and if none exists, the command"
+              + " will result in failure.")
   public boolean fetch;
 
   @Option(