cmd/go-cache-plugin: update "help environment" text

Author: creachadair

cmd/go-cache-plugin/go-cache-plugin.go

@@ -71,19 +71,27 @@ listening on a socket.`,
 To make it easier to configure this tool for multiple workflows, most of the
 settings can be set via environment variables as well as flags.
 
-    Flag              Variable               Format    Default
-    --cache-dir       GOCACHE_DIR            path      (required)
-    --bucket          GOCACHE_S3_BUCKET      string    (required)
-    --region          GOCACHE_S3_REGION      string    based on bucket
-    --prefix          GOCACHE_KEY_PREFIX     string    ""
-    --min-upload-size GOCACHE_MIN_SIZE       int64     0
-    --metrics         GOCACHE_METRICS        bool      false
-    --expiry          GOCACHE_EXPIRY         duration  0
-    --socket          GOCACHE_SOCKET         path      (required for "serve")
-    -c                GOCACHE_CONCURRENCY    int       runtime.NumCPU
-    -u                GOCACHE_S3_CONCURRENCY duration  runtime.NumCPU
-    -v                GOCACHE_VERBOSE        bool      false
-    --debug           GOCACHE_DEBUG          bool      false
+   --------------------------------------------------------------------
+   Flag (global)      Variable               Format      Default
+   --------------------------------------------------------------------
+    --cache-dir       GOCACHE_DIR            path        (required)
+    --bucket          GOCACHE_S3_BUCKET      string      (required)
+    --region          GOCACHE_S3_REGION      string      based on bucket
+    --prefix          GOCACHE_KEY_PREFIX     string      ""
+    --min-upload-size GOCACHE_MIN_SIZE       int64       0
+    --metrics         GOCACHE_METRICS        bool        false
+    --expiry          GOCACHE_EXPIRY         duration    0
+    -c                GOCACHE_CONCURRENCY    int         runtime.NumCPU
+    -u                GOCACHE_S3_CONCURRENCY duration    runtime.NumCPU
+    -v                GOCACHE_VERBOSE        bool        false
+    --debug           GOCACHE_DEBUG          bool        false
+
+   --------------------------------------------------------------------
+   Flag (serve)       Variable               Format      Default
+   --------------------------------------------------------------------
+    --socket          GOCACHE_SOCKET         path        (required)
+    --modproxy        GOCACHE_MODPROXY       [host]:port ""
+    --sumdb           GOCACHE_SUMDB          host,...    ""
 `,
 			}}),
 			command.VersionCommand(),