internal/version: drop manual VCS version code

Go 1.24 started stamping local builds from a VCS clone with proper
version information for the main module. Before the changes:

    $ go install
    $ gofumpt -version
    v0.8.1-0.20250831000946-c75c2d2e49fb (go1.26-devel_8bcda6c79d 2025-08-29 23:57:12 -0700)

And after the changes in a dirty state:

    $ go install
    $ gofumpt -version
    v0.8.1-0.20250831000946-c75c2d2e49fb+dirty (go1.26-devel_8bcda6c79d 2025-08-29 23:57:12 -0700)

Author: mvdan

internal/version/version.go

@@ -4,23 +4,14 @@
 package version
 
 import (
-	"encoding/json"
 	"fmt"
 	"os"
 	"runtime"
 	"runtime/debug"
-	"time"
-
-	"golang.org/x/mod/module"
 )
 
-// Note that this is not a main package, so a "var version" will not work with
-// our go-cross script which uses -ldflags=main.version=xxx.
-
 const ourModulePath = "mvdan.cc/gofumpt"
 
-const fallbackVersion = "(devel)" // to match the default from runtime/debug
-
 func findModule(info *debug.BuildInfo, modulePath string) *debug.Module {
 	if info.Main.Path == modulePath {
 		return &info.Main
@@ -36,57 +27,18 @@ func findModule(info *debug.BuildInfo, modulePath string) *debug.Module {
 func gofumptVersion() string {
 	info, ok := debug.ReadBuildInfo()
 	if !ok {
-		return fallbackVersion // no build info available
+		return "(no build info)"
 	}
 	// Note that gofumpt may be used as a library via the format package,
 	// so we cannot assume it is the main module in the build.
 	mod := findModule(info, ourModulePath)
 	if mod == nil {
-		return fallbackVersion // not found?
+		return "(module not found)"
 	}
 	if mod.Replace != nil {
 		mod = mod.Replace
 	}
-
-	// If we found a meaningful version, we are done.
-	// If gofumpt is not the main module, stop as well,
-	// as VCS info is only for the main module.
-	if mod.Version != "(devel)" || mod != &info.Main {
-		return mod.Version
-	}
-
-	// Fall back to trying to use VCS information.
-	// Until https://github.com/golang/go/issues/50603 is implemented,
-	// manually construct something like a pseudo-version.
-	// TODO: remove when this code is dead, hopefully in Go 1.20.
-
-	// For the tests, as we don't want the VCS information to change over time.
-	if v := os.Getenv("GARBLE_TEST_BUILDSETTINGS"); v != "" {
-		var extra []debug.BuildSetting
-		if err := json.Unmarshal([]byte(v), &extra); err != nil {
-			panic(err)
-		}
-		info.Settings = append(info.Settings, extra...)
-	}
-
-	var vcsTime time.Time
-	var vcsRevision string
-	for _, setting := range info.Settings {
-		switch setting.Key {
-		case "vcs.time":
-			// If the format is invalid, we'll print a zero timestamp.
-			vcsTime, _ = time.Parse(time.RFC3339Nano, setting.Value)
-		case "vcs.revision":
-			vcsRevision = setting.Value
-			if len(vcsRevision) > 12 {
-				vcsRevision = vcsRevision[:12]
-			}
-		}
-	}
-	if vcsRevision != "" {
-		return module.PseudoVersion("", "", vcsTime, vcsRevision)
-	}
-	return fallbackVersion
+	return mod.Version
 }
 
 func goVersion() string {

testdata/script/diagnose.txtar

@@ -1,10 +1,7 @@
+# Note that `go test` binaries don't get stamped with versions,
+# so the local tests below end up with a "devel" gofumpt version.
 env GO_VERSION_TEST=go1.18.29
 
-# First, test a local build of gofumpt resulting from 'git clone'.
-# Its version will be inferred from VCS, but since we want a stable test,
-# we mock the VCS information. Note that test binaries do not have VCS info.
-# Data obtained from a real build while developing.
-env GARBLE_TEST_BUILDSETTINGS='[{"Key":"vcs","Value":"git"},{"Key":"vcs.revision","Value":"8dda8068d9f339047fc1777b688afb66a0a0db17"},{"Key":"vcs.time","Value":"2022-07-27T15:58:40Z"},{"Key":"vcs.modified","Value":"true"}]'  
 exec gofumpt foo.go
 cmp stdout foo.go.golden
 
@@ -26,11 +23,6 @@ exec gofumpt -d foo.go.golden
 exec gofumpt -d -extra foo.go.golden-extra
 ! stdout .
 
-# A local build without VCS information will result in a missing version.
-env GARBLE_TEST_BUILDSETTINGS='[]'
-exec gofumpt foo.go
-cmp stdout foo.go.golden-devel
-
 [short] stop 'the rest of this test builds gofumpt binaries'
 
 # We want a published version of gofumpt on the public module proxies,
@@ -80,19 +72,15 @@ package p
 -- foo.go.golden --
 package p
 
-//gofumpt:diagnose version: v0.0.0-20220727155840-8dda8068d9f3 (go1.18.29) flags: -lang=go1.16 -modpath=test
--- foo.go.golden-devel --
-package p
-
 //gofumpt:diagnose version: (devel) (go1.18.29) flags: -lang=go1.16 -modpath=test
 -- foo.go.golden-extra --
 package p
 
-//gofumpt:diagnose version: v0.0.0-20220727155840-8dda8068d9f3 (go1.18.29) flags: -lang=go1.16 -modpath=test -extra
+//gofumpt:diagnose version: (devel) (go1.18.29) flags: -lang=go1.16 -modpath=test -extra
 -- foo.go.golden-lang --
 package p
 
-//gofumpt:diagnose version: v0.0.0-20220727155840-8dda8068d9f3 (go1.18.29) flags: -lang=go1 -modpath=test
+//gofumpt:diagnose version: (devel) (go1.18.29) flags: -lang=go1 -modpath=test
 -- foo.go.golden-released --
 package p