refactor(depotfmt): Move formatting check into an extra step

Change-Id: I7e4cf6bb2351bd11a5396f1663c0d4cc97c0d94e
Reviewed-on: https://cl.tvl.fyi/c/depot/+/5009
Tested-by: BuildkiteCI
Reviewed-by: sterni <sternenseemann@systemli.org>
Reviewed-by: grfn <grfn@gws.fyi>
Reviewed-by: ezemtsov <eugene.zemtsov@gmail.com>

ops/pipelines/depot.nix

@@ -11,17 +11,10 @@ let
     label = ":water_buffalo:";
   };
 
-  # Formatting check which validates that all supported auto-formatted
-  # files are formatted correctly. See //tools/depotfmt for details.
-  depotfmtCheck = {
-    command = "${depot.tools.depotfmt.check}";
-    label = ":evergreen_tree: (tools/depotfmt)";
-  };
-
   pipeline = depot.nix.buildkite.mkPipeline {
     headBranch = "refs/heads/canon";
     drvTargets = depot.ci.targets;
-    additionalSteps = [ depotfmtCheck protoCheck ];
+    additionalSteps = [ protoCheck ];
 
     parentTargetMap = if (externalArgs ? parentTargetMap)
       then builtins.fromJSON (builtins.readFile externalArgs.parentTargetMap)

tools/depotfmt.nix

@@ -35,5 +35,9 @@ let
       --tree-root .
   '';
 in depotfmt.overrideAttrs(_: {
-  passthru.check = check;
+  passthru.meta.ci.extraSteps.check = {
+    label = "depot formatting check";
+    command = check;
+    alwaysRun = true;
+  };
 })