cli: classify ssh cache errors in DiskCache

src/cli/ssh-cache/DiskCache.zig

@@ -393,6 +393,16 @@ fn readEntries(
     return entries;
 }
 
+/// Whether an error from a cache operation reflects a problem with the cache
+/// itself. A destination we can't key on and a lock held by another process
+/// both leave the cache healthy, so neither is worth reporting.
+pub fn isFailure(err: anyerror) bool {
+    return switch (err) {
+        error.InvalidCacheKey, error.CacheLocked => false,
+        else => true,
+    };
+}
+
 // Supports both standalone hostnames and user@hostname format
 pub fn isValidCacheKey(key: []const u8) bool {
     if (key.len == 0) return false;
@@ -704,6 +714,15 @@ test "disk cache add survives allocation failure" {
     }
 }
 
+test isFailure {
+    const testing = std.testing;
+
+    try testing.expect(!isFailure(error.InvalidCacheKey));
+    try testing.expect(!isFailure(error.CacheLocked));
+    try testing.expect(isFailure(error.AccessDenied));
+    try testing.expect(isFailure(error.IsDir));
+}
+
 test isValidHost {
     const testing = std.testing;
 

src/cli/ssh.zig

@@ -253,10 +253,9 @@ fn runInner(
 
         if (cache) |c| {
             const cached = c.contains(alloc, dest) catch |err| cached: {
-                // An invalid key is a bad destination, not a bad cache.
-                if (err != error.InvalidCacheKey) warnPrint(
+                if (DiskCache.isFailure(err)) warnPrint(
                     stderr,
-                    "unable to add '{s}' to the cache: {t}",
+                    "unable to read the cache '{s}': {t}",
                     .{ c.path, err },
                 );
                 break :cached false;
@@ -319,23 +318,21 @@ fn runInner(
             .real,
         ).toSeconds())) |_| {
             verbosePrint(opts, stderr, "cache: wrote {s}", .{entry.dest});
-        } else |err| switch (err) {
-            // An uncacheable destination was already reported above, and a
-            // lock held by a concurrent `+ssh` resolves itself.
-            error.InvalidCacheKey,
-            error.CacheLocked,
-            => verbosePrint(
-                opts,
-                stderr,
-                "cache: skipped {s}: {t}",
-                .{ entry.dest, err },
-            ),
-
-            else => warnPrint(
-                stderr,
-                "unable to add '{s}' to the cache '{s}': {t}",
-                .{ entry.dest, entry.cache.path, err },
-            ),
+        } else |err| {
+            if (DiskCache.isFailure(err)) {
+                warnPrint(
+                    stderr,
+                    "unable to add '{s}' to the cache '{s}': {t}",
+                    .{ entry.dest, entry.cache.path, err },
+                );
+            } else {
+                verbosePrint(
+                    opts,
+                    stderr,
+                    "cache: skipped {s}: {t}",
+                    .{ entry.dest, err },
+                );
+            }
         }
     };