[tint] Add --update-skip E2E test runner option

The `--generate-skip` option is usually used to generate skip files
for newly added tests. It currently also updates all existing skip
files, which makes CLs very noisy.

This CL changes the behavior to only generate new skip files, and adds
a new `--update-skip` option that can be used to regenerate existing
skip files instead.

Fixed: 430290761
No-Try: true
Change-Id: Ifc9df88a2066e445338378b4e717f13ec0f86f35
Reviewed-on: https://dawn-review.googlesource.com/c/dawn/+/283455
Auto-Submit: James Price <jrprice@google.com>
Commit-Queue: dan sinclair <dsinclair@chromium.org>
Reviewed-by: dan sinclair <dsinclair@chromium.org>

tools/src/cmd/tests/main.go

diff --git a/tools/src/cmd/tests/main.go b/tools/src/cmd/tests/main.go
index 82e6d75..5cc2077 100644
--- a/tools/src/cmd/tests/main.go
+++ b/tools/src/cmd/tests/main.go
@@ -142,7 +142,7 @@
 	var maxTableWidth int
 	var server bool
 	numCPU := runtime.NumCPU()
-	verbose, generateExpected, generateSkip := false, false, false
+	verbose, generateExpected, generateSkip, updateSkip := false, false, false, false
 	flag.StringVar(&formatList, "format", "all", "comma separated list of formats to emit. Possible values are: all, wgsl, spvasm, msl, hlsl, hlsl-dxc, hlsl-fxc, glsl")
 	flag.StringVar(&ignore, "ignore", "**.expected.*", "files to ignore in globs")
 	flag.StringVar(&dxcPath, "dxcompiler", "", "path to DXC DLL for validating HLSL output")
@@ -151,7 +151,8 @@
 	flag.StringVar(&xcrunPath, "xcrun", "", "path to xcrun executable for validating MSL output")
 	flag.BoolVar(&verbose, "verbose", false, "print all run tests, including rows that all pass")
 	flag.BoolVar(&generateExpected, "generate-expected", false, "create or update all expected outputs")
-	flag.BoolVar(&generateSkip, "generate-skip", false, "create or update all expected outputs that fail with SKIP")
+	flag.BoolVar(&generateSkip, "generate-skip", false, "create new expected outputs that fail with SKIP")
+	flag.BoolVar(&updateSkip, "update-skip", false, "update all expected outputs that fail with SKIP")
 	flag.BoolVar(&server, "server", true, "run Tint in server mode")
 	flag.IntVar(&numCPU, "j", numCPU, "maximum number of concurrent threads to run tests")
 	flag.IntVar(&maxTableWidth, "table-width", terminalWidth, "maximum width of the results table")
@@ -329,6 +330,7 @@
 		xcrunPath:        xcrunPath,
 		generateExpected: generateExpected,
 		generateSkip:     generateSkip,
+		updateSkip:       updateSkip,
 		validationCache:  validationCache,
 		server:           server,
 	}
@@ -669,6 +671,7 @@
 	xcrunPath        string
 	generateExpected bool
 	generateSkip     bool
+	updateSkip       bool
 	validationCache  validationCache
 	server           bool
 }
@@ -726,7 +729,7 @@
 		}
 
 		// If the test is known to fail and we are not regenerating expectations, just skip the test.
-		if isSkipTest && !cfg.generateExpected && !cfg.generateSkip {
+		if isSkipTest && !cfg.generateExpected && !cfg.updateSkip {
 			if isSkipInvalidTest {
 				return status{code: invalid, timeTaken: 0}
 			} else {
@@ -852,7 +855,7 @@
 			//       --- Below this point the test has failed ---
 		case isSkipTest:
 			// Do not update expected if timeout test actually timed out.
-			if cfg.generateSkip && !(isSkipTimeoutTest && timedOut) {
+			if cfg.updateSkip && !(isSkipTimeoutTest && timedOut) {
 				saveExpectedFile(expectedFilePath, "SKIP: "+skipStr+"\n\n"+out)
 			}
 			if isSkipInvalidTest {