version: use OSS repo's version when building.

When building with redo, also include the git commit hash
from the proprietary repo, so that we have a precise commit
that identifies all build info (including Go toolchain version).

Add a top-level build script demonstrating to downstream distros
how to burn the right information into builds.

Adjust `tailscale version` to print commit hashes when available.

Fixes #841.

Signed-off-by: David Anderson <danderson@tailscale.com>

README.md

@@ -30,6 +30,18 @@ wrappers that are not open source.
 go install tailscale.com/cmd/tailscale{,d}
 ```
 
+If you're packaging Tailscale for distribution, use `build_dist.sh`
+instead, to burn commit IDs and version info into the binaries:
+
+```
+./build_dist.sh tailscale.com/cmd/tailscale
+./build_dist.sh tailscale.com/cmd/tailscaled
+```
+
+If your distro has conventions that preclude the use of
+`build_dist.sh`, please do the equivalent of what it does in your
+distro's way, so that bug reports contain useful version information.
+
 We only guarantee to support the latest Go release and any Go beta or
 release candidate builds (currently Go 1.15) in module mode. It might
 work in earlier Go versions or in GOPATH mode, but we're making no

build_dist.sh

@@ -0,0 +1,22 @@
+#!/usr/bin/env sh
+#
+# Runs `go build` with flags configured for binary distribution. All
+# it does differently from `go build` is burn git commit and version
+# information into the binaries, so that we can track down user
+# issues.
+#
+# If you're packaging Tailscale for a distro, please consider using
+# this script, or executing equivalent commands in your
+# distro-specific build system.
+
+set -euo pipefail
+
+describe=$(git describe --long --abbrev=9)
+# --abbrev=200 is an arbitrary large number to capture the entire git
+# hash without trying to compact it.
+commit=$(git describe --dirty --exclude "*" --always --abbrev=200)
+
+long=$(./version/mkversion.sh long "$describe" "")
+short=$(./version/mkversion.sh short "$describe" "")
+
+exec go build -tags xversion -ldflags "-X tailscale.com/version.Long=${long} -X tailscale.com/version.Short=${short} -X tailscale.com/version.GitCommit=${commit}" "$@"

cmd/derper/derper.go

@@ -233,7 +233,7 @@ func debugHandler(s *derp.Server) http.Handler {
 		f("<li><b>Hostname:</b> %v</li>\n", html.EscapeString(*hostname))
 		f("<li><b>Uptime:</b> %v</li>\n", tsweb.Uptime())
 		f("<li><b>Mesh Key:</b> %v</li>\n", s.HasMeshKey())
-		f("<li><b>Version:</b> %v</li>\n", html.EscapeString(version.LONG))
+		f("<li><b>Version:</b> %v</li>\n", html.EscapeString(version.Long))
 
 		f(`<li><a href="/debug/vars">/debug/vars</a> (Go)</li>
    <li><a href="/debug/varz">/debug/varz</a> (Prometheus)</li>

cmd/tailscale/cli/version.go

@@ -36,10 +36,11 @@ func runVersion(ctx context.Context, args []string) error {
 		log.Fatalf("too many non-flag arguments: %q", args)
 	}
 	if !versionArgs.daemon {
-		fmt.Println(version.LONG)
+		fmt.Println(version.String())
 		return nil
 	}
-	fmt.Printf("Client: %s\n", version.LONG)
+
+	fmt.Printf("Client: %s\n", version.String())
 
 	c, bc, ctx, cancel := connect(ctx)
 	defer cancel()

cmd/tailscaled/depaware.txt

@@ -84,7 +84,7 @@ tailscale.com/cmd/tailscaled dependencies: (generated by github.com/tailscale/de
         tailscale.com/types/structs                                  from tailscale.com/control/controlclient+
         tailscale.com/util/lineread                                  from tailscale.com/control/controlclient+
         tailscale.com/util/pidowner                                  from tailscale.com/ipn/ipnserver
-        tailscale.com/version                                        from tailscale.com/control/controlclient+
+        tailscale.com/version                                        from tailscale.com/cmd/tailscaled+
         tailscale.com/version/distro                                 from tailscale.com/control/controlclient+
         tailscale.com/wgengine                                       from tailscale.com/cmd/tailscaled+
         tailscale.com/wgengine/filter                                from tailscale.com/control/controlclient+

cmd/tailscaled/tailscaled.go

@@ -12,6 +12,7 @@ package main // import "tailscale.com/cmd/tailscaled"
 import (
 	"context"
 	"flag"
+	"fmt"
 	"log"
 	"net/http"
 	"net/http/pprof"
@@ -29,6 +30,7 @@ import (
 	"tailscale.com/paths"
 	"tailscale.com/types/flagtype"
 	"tailscale.com/types/logger"
+	"tailscale.com/version"
 	"tailscale.com/wgengine"
 	"tailscale.com/wgengine/magicsock"
 	"tailscale.com/wgengine/router"
@@ -73,6 +75,7 @@ func main() {
 		debug.SetGCPercent(10)
 	}
 
+	printVersion := false
 	flag.BoolVar(&args.cleanup, "cleanup", false, "clean up system state and exit")
 	flag.BoolVar(&args.fake, "fake", false, "use userspace fake tunnel+routing instead of kernel TUN interface")
 	flag.StringVar(&args.debug, "debug", "", "listen address ([ip]:port) of optional debug server")
@@ -80,6 +83,7 @@ func main() {
 	flag.Var(flagtype.PortValue(&args.port, magicsock.DefaultPort), "port", "UDP port to listen on for WireGuard and peer-to-peer traffic; 0 means automatically select")
 	flag.StringVar(&args.statepath, "state", paths.DefaultTailscaledStateFile(), "path of state file")
 	flag.StringVar(&args.socketpath, "socket", paths.DefaultTailscaledSocket(), "path of the service unix socket")
+	flag.BoolVar(&printVersion, "version", false, "print version information and exit")
 
 	err := fixconsole.FixConsoleIfNeeded()
 	if err != nil {
@@ -91,6 +95,11 @@ func main() {
 		log.Fatalf("tailscaled does not take non-flag arguments: %q", flag.Args())
 	}
 
+	if printVersion {
+		fmt.Println(version.String())
+		os.Exit(0)
+	}
+
 	if args.statepath == "" {
 		log.Fatalf("--state is required")
 	}

control/controlclient/direct.go

@@ -206,7 +206,7 @@ func NewHostinfo() *tailcfg.Hostinfo {
 		osv = osVersion()
 	}
 	return &tailcfg.Hostinfo{
-		IPNVersion: version.LONG,
+		IPNVersion: version.Long,
 		Hostname:   hostname,
 		OS:         version.OS(),
 		OSVersion:  osv,

derp/derp_server.go

@@ -1291,7 +1291,7 @@ func (s *Server) ExpVar() expvar.Var {
 	m.Set("multiforwarder_deleted", &s.multiForwarderDeleted)
 	m.Set("packet_forwarder_delete_other_value", &s.removePktForwardOther)
 	var expvarVersion expvar.String
-	expvarVersion.Set(version.LONG)
+	expvarVersion.Set(version.Long)
 	m.Set("version", &expvarVersion)
 	return m
 }

ipn/ipnserver/server.go

@@ -473,7 +473,7 @@ func Run(ctx context.Context, logf logger.Logf, logid string, getEngine func() (
 
 	if opts.AutostartStateKey != "" {
 		server.bs.GotCommand(&ipn.Command{
-			Version: version.LONG,
+			Version: version.Long,
 			Start: &ipn.StartArgs{
 				Opts: ipn.Options{
 					StateKey:         opts.AutostartStateKey,

ipn/local.go

@@ -671,7 +671,7 @@ func (b *LocalBackend) send(n Notify) {
 	b.mu.Unlock()
 
 	if notify != nil {
-		n.Version = version.LONG
+		n.Version = version.Long
 		notify(n)
 	} else {
 		b.logf("nil notify callback; dropping %+v", n)
@@ -945,7 +945,7 @@ func (b *LocalBackend) parseWgStatus(s *wgengine.Status) (ret EngineStatus) {
 		// [GRINDER STATS LINE] - please don't remove (used for log parsing)
 		b.keyLogf("peer keys: %s", strings.Join(peerKeys, " "))
 		// [GRINDER STATS LINE] - please don't remove (used for log parsing)
-		b.logf("v%v peers: %v", version.LONG, strings.Join(peerStats, " "))
+		b.logf("v%v peers: %v", version.Long, strings.Join(peerStats, " "))
 	}
 	return ret
 }

ipn/message.go

@@ -80,7 +80,7 @@ func NewBackendServer(logf logger.Logf, b Backend, sendNotifyMsg func(b []byte))
 }
 
 func (bs *BackendServer) send(n Notify) {
-	n.Version = version.LONG
+	n.Version = version.Long
 	b, err := json.Marshal(n)
 	if err != nil {
 		log.Fatalf("Failed json.Marshal(notify): %v\n%#v", err, n)
@@ -106,14 +106,14 @@ func (bs *BackendServer) GotCommandMsg(b []byte) error {
 }
 
 func (bs *BackendServer) GotFakeCommand(cmd *Command) error {
-	cmd.Version = version.LONG
+	cmd.Version = version.Long
 	return bs.GotCommand(cmd)
 }
 
 func (bs *BackendServer) GotCommand(cmd *Command) error {
-	if cmd.Version != version.LONG && !cmd.AllowVersionSkew {
+	if cmd.Version != version.Long && !cmd.AllowVersionSkew {
 		vs := fmt.Sprintf("GotCommand: Version mismatch! frontend=%#v backend=%#v",
-			cmd.Version, version.LONG)
+			cmd.Version, version.Long)
 		bs.logf("%s", vs)
 		// ignore the command, but send a message back to the
 		// caller so it can realize the version mismatch too.
@@ -197,9 +197,9 @@ func (bc *BackendClient) GotNotifyMsg(b []byte) {
 	if err := json.Unmarshal(b, &n); err != nil {
 		log.Fatalf("BackendClient.Notify: cannot decode message (length=%d)\n%#v", len(b), string(b))
 	}
-	if n.Version != version.LONG && !bc.AllowVersionSkew {
+	if n.Version != version.Long && !bc.AllowVersionSkew {
 		vs := fmt.Sprintf("GotNotify: Version mismatch! frontend=%#v backend=%#v",
-			version.LONG, n.Version)
+			version.Long, n.Version)
 		bc.logf("%s", vs)
 		// delete anything in the notification except the version,
 		// to prevent incorrect operation.
@@ -214,7 +214,7 @@ func (bc *BackendClient) GotNotifyMsg(b []byte) {
 }
 
 func (bc *BackendClient) send(cmd Command) {
-	cmd.Version = version.LONG
+	cmd.Version = version.Long
 	b, err := json.Marshal(cmd)
 	if err != nil {
 		log.Fatalf("Failed json.Marshal(cmd): %v\n%#v\n", err, cmd)

logpolicy/logpolicy.go

@@ -395,7 +395,7 @@ func New(collection string) *Policy {
 	log.SetOutput(lw)
 
 	log.Printf("Program starting: v%v, Go %v: %#v",
-		version.LONG,
+		version.Long,
 		strings.TrimPrefix(runtime.Version(), "go"),
 		os.Args)
 	log.Printf("LogID: %v", newc.PublicID)

version/.gitignore

@@ -1,6 +1,8 @@
 describe.txt
 long.txt
 short.txt
+gitcommit.txt
+extragitcommit.txt
 version.h
 version.xcconfig
 ver.go

version/describe.txt.do

@@ -1,4 +1,4 @@
-describe=$(cd ../.. && git describe --long --abbrev=9)
+describe=$(git describe --long --abbrev=9)
 echo "$describe" >$3
 redo-always
 redo-stamp <$3

version/extragitcommit.txt.do

@@ -0,0 +1,6 @@
+# --abbrev=200 is an arbitrary large number to capture the entire git
+# hash without trying to compact it.
+commit=$(cd ../.. && git describe --dirty --exclude "*" --always --abbrev=200)
+echo "$commit" >$3
+redo-always
+redo-stamp <$3

version/gitcommit.txt.do

@@ -0,0 +1,6 @@
+# --abbrev=200 is an arbitrary large number to capture the entire git
+# hash without trying to compact it.
+commit=$(git describe --dirty --exclude "*" --always --abbrev=200)
+echo "$commit" >$3
+redo-always
+redo-stamp <$3

version/long.txt.do

@@ -1,4 +1,5 @@
-redo-ifchange mkversion.sh describe.txt
+redo-ifchange mkversion.sh describe.txt extragitcommit.txt
 read -r describe <describe.txt
-ver=$(./mkversion.sh long "$describe")
+read -r other <extragitcommit.txt
+ver=$(./mkversion.sh long "$describe" "$other")
 echo "$ver" >$3

version/mkversion.sh

@@ -4,6 +4,7 @@ set -eu
 
 mode=$1
 describe=$2
+other=$3
 
 # Git describe output overall looks like
 # MAJOR.MINOR.PATCH-NUMCOMMITS-GITHASH. Depending on the tag being
@@ -55,6 +56,25 @@ case "$suffix" in
         ;;
 esac
 
+# The git hash is of the form "gCOMMITHASH". We want to replace the
+# 'g' with a 't', for "tailscale", to convey that it's specifically
+# the commit hash of the tailscale repo.
+if [ -n "$githash" ]; then
+    # POSIX shell doesn't understand ${foo:1:9} syntax, gaaah.
+    githash="$(echo $githash | cut -c2-10)"
+    githash="t${githash}"
+fi
+
+# "other" is a second git commit hash for another repository used to
+# build the Tailscale code. In practice it's either the commit hash in
+# the Android repository, or the commit hash of Tailscale's
+# proprietary repository (which pins a bunch things like build scripts
+# used and Go toolchain version).
+if [ -n "$other" ]; then
+    other="$(echo $other | cut -c1-9)"
+    other="-o${other}"
+fi
+
 # Validate that the version data makes sense. Rules:
 #  - Odd number minors are unstable. Patch must be 0, and gets
 #    replaced by changecount.
@@ -82,15 +102,23 @@ else
         # pbulic, but it's useful to be able to build it for
         # debugging. Just force the version to 0.0.0, so that we're
         # forced to rely on the git commit hash.
-        major=0
-        minor=0
-        patch=0
+        major="0"
+        minor="0"
+        patch="0"
     fi
 fi
 
+if [ "$minor" -eq 1 ]; then
+    # Hack for 1.1: add 1000 to the patch number, so that builds that
+    # use the OSS change count order after the builds that used the
+    # proprietary repo's changecount. Otherwise, the version numbers
+    # would go backwards and things would be unhappy.
+    patch=$((patch + 1000))
+fi
+
 case "$1" in
     long)
-        echo "${major}.${minor}.${patch}-${githash}"
+        echo "${major}.${minor}.${patch}-${githash}${other}"
         ;;
     short)
         echo "${major}.${minor}.${patch}"

version/mkversion_test.go

@@ -16,9 +16,9 @@ func xcode(short, long string) string {
 	return fmt.Sprintf("VERSION_NAME = %s\nVERSION_ID = %s", short, long)
 }
 
-func mkversion(t *testing.T, mode, in string) (string, bool) {
+func mkversion(t *testing.T, mode, describe, other string) (string, bool) {
 	t.Helper()
-	bs, err := exec.Command("./mkversion.sh", mode, in).CombinedOutput()
+	bs, err := exec.Command("./mkversion.sh", mode, describe, other).CombinedOutput()
 	if err != nil {
 		t.Logf("mkversion.sh output: %s", string(bs))
 		return "", false
@@ -31,49 +31,50 @@ func TestMkversion(t *testing.T) {
 		t.Skip("skip test on Windows, because there is no shell to execute mkversion.sh.")
 	}
 	tests := []struct {
-		in    string
-		ok    bool
-		long  string
-		short string
-		xcode string
+		describe string
+		other    string
+		ok       bool
+		long     string
+		short    string
+		xcode    string
 	}{
-		{"v0.98-abcdef", true, "0.98.0-abcdef", "0.98.0", xcode("0.98.0", "100.98.0")},
-		{"v0.98.1-abcdef", true, "0.98.1-abcdef", "0.98.1", xcode("0.98.1", "100.98.1")},
-		{"v1.1.0-37-abcdef", true, "1.1.37-abcdef", "1.1.37", xcode("1.1.37", "101.1.37")},
-		{"v1.2.9-abcdef", true, "1.2.9-abcdef", "1.2.9", xcode("1.2.9", "101.2.9")},
-		{"v1.2.9-0-abcdef", true, "1.2.9-abcdef", "1.2.9", xcode("1.2.9", "101.2.9")},
-		{"v1.15.0-129-abcdef", true, "1.15.129-abcdef", "1.15.129", xcode("1.15.129", "101.15.129")},
+		{"v0.98-gabcdef", "", true, "0.98.0-tabcdef", "0.98.0", xcode("0.98.0", "100.98.0")},
+		{"v0.98.1-gabcdef", "", true, "0.98.1-tabcdef", "0.98.1", xcode("0.98.1", "100.98.1")},
+		{"v1.1.0-37-gabcdef", "", true, "1.1.1037-tabcdef", "1.1.1037", xcode("1.1.1037", "101.1.1037")},
+		{"v1.2.9-gabcdef", "", true, "1.2.9-tabcdef", "1.2.9", xcode("1.2.9", "101.2.9")},
+		{"v1.2.9-0-gabcdef", "", true, "1.2.9-tabcdef", "1.2.9", xcode("1.2.9", "101.2.9")},
+		{"v1.15.0-129-gabcdef", "", true, "1.15.129-tabcdef", "1.15.129", xcode("1.15.129", "101.15.129")},
 
-		{"v0.98-123-abcdef", true, "0.0.0-abcdef", "0.0.0", xcode("0.0.0", "100.0.0")},
-		{"v1.0.0-37-abcdef", true, "0.0.0-abcdef", "0.0.0", xcode("0.0.0", "100.0.0")},
-
-		{"v0.99.5-0-abcdef", false, "", "", ""},   // unstable, patch not allowed
-		{"v0.99.5-123-abcdef", false, "", "", ""}, // unstable, patch not allowed
-		{"v1-abcdef", false, "", "", ""},          // bad semver
-		{"v1.0", false, "", "", ""},               // missing suffix
+		{"v0.98-123-gabcdef", "", true, "0.0.0-tabcdef", "0.0.0", xcode("0.0.0", "100.0.0")},
+		{"v1.0.0-37-gabcdef", "", true, "0.0.0-tabcdef", "0.0.0", xcode("0.0.0", "100.0.0")},
+		{"v1.1.0-129-gabcdef", "0123456789abcdef0123456789abcdef", true, "1.1.1129-tabcdef-o012345678", "1.1.1129", xcode("1.1.1129", "101.1.1129")},
+		{"v0.99.5-0-gabcdef", "", false, "", "", ""},   // unstable, patch not allowed
+		{"v0.99.5-123-gabcdef", "", false, "", "", ""}, // unstable, patch not allowed
+		{"v1-gabcdef", "", false, "", "", ""},          // bad semver
+		{"v1.0", "", false, "", "", ""},                // missing suffix
 	}
 
 	for _, test := range tests {
-		gotlong, longOK := mkversion(t, "long", test.in)
+		gotlong, longOK := mkversion(t, "long", test.describe, test.other)
 		if longOK != test.ok {
-			t.Errorf("mkversion.sh long %q ok=%v, want %v", test.in, longOK, test.ok)
+			t.Errorf("mkversion.sh long %q ok=%v, want %v", test.describe, longOK, test.ok)
 		}
-		gotshort, shortOK := mkversion(t, "short", test.in)
+		gotshort, shortOK := mkversion(t, "short", test.describe, test.other)
 		if shortOK != test.ok {
-			t.Errorf("mkversion.sh short %q ok=%v, want %v", test.in, shortOK, test.ok)
+			t.Errorf("mkversion.sh short %q ok=%v, want %v", test.describe, shortOK, test.ok)
 		}
-		gotxcode, xcodeOK := mkversion(t, "xcode", test.in)
+		gotxcode, xcodeOK := mkversion(t, "xcode", test.describe, test.other)
 		if xcodeOK != test.ok {
-			t.Errorf("mkversion.sh xcode %q ok=%v, want %v", test.in, xcodeOK, test.ok)
+			t.Errorf("mkversion.sh xcode %q ok=%v, want %v", test.describe, xcodeOK, test.ok)
 		}
 		if longOK && gotlong != test.long {
-			t.Errorf("mkversion.sh long %q: got %q, want %q", test.in, gotlong, test.long)
+			t.Errorf("mkversion.sh long %q: got %q, want %q", test.describe, gotlong, test.long)
 		}
 		if shortOK && gotshort != test.short {
-			t.Errorf("mkversion.sh short %q: got %q, want %q", test.in, gotshort, test.short)
+			t.Errorf("mkversion.sh short %q: got %q, want %q", test.describe, gotshort, test.short)
 		}
 		if xcodeOK && gotxcode != test.xcode {
-			t.Errorf("mkversion.sh xcode %q: got %q, want %q", test.in, gotxcode, test.xcode)
+			t.Errorf("mkversion.sh xcode %q: got %q, want %q", test.describe, gotxcode, test.xcode)
 		}
 	}
 }

version/print.go

@@ -0,0 +1,25 @@
+// Copyright (c) 2020 Tailscale Inc & AUTHORS All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package version
+
+import (
+	"fmt"
+	"runtime"
+	"strings"
+)
+
+func String() string {
+	var ret strings.Builder
+	ret.WriteString(Short)
+	ret.WriteByte('\n')
+	if GitCommit != "" {
+		fmt.Fprintf(&ret, "  tailscale commit: %s\n", GitCommit)
+	}
+	if ExtraGitCommit != "" {
+		fmt.Fprintf(&ret, "  other commit: %s\n", ExtraGitCommit)
+	}
+	fmt.Fprintf(&ret, "  go version: %s\n", runtime.Version())
+	return strings.TrimSpace(ret.String())
+}

version/short.txt.do

@@ -1,4 +1,5 @@
-redo-ifchange mkversion.sh describe.txt
+redo-ifchange mkversion.sh describe.txt extragitcommit.txt
 read -r describe <describe.txt
-ver=$(./mkversion.sh short "$describe")
+read -r other <extragitcommit.txt
+ver=$(./mkversion.sh short "$describe" "$other")
 echo "$ver" >$3

version/ver.go.do

@@ -1,8 +1,12 @@
-redo-ifchange long.txt short.txt ver.go.in
+redo-ifchange long.txt short.txt gitcommit.txt extragitcommit.txt ver.go.in
 
 read -r LONGVER <long.txt
 read -r SHORTVER <short.txt
+read -r GITCOMMIT <gitcommit.txt
+read -r EXTRAGITCOMMIT <extragitcommit.txt
 
 sed -e "s/{LONGVER}/$LONGVER/g" \
     -e "s/{SHORTVER}/$SHORTVER/g" \
+    -e "s/{GITCOMMIT}/$GITCOMMIT/g" \
+    -e "s/{EXTRAGITCOMMIT}/$EXTRAGITCOMMIT/g" \
     <ver.go.in >$3

version/ver.go.in

@@ -6,5 +6,9 @@
 
 package version
 
-const LONG = "{LONGVER}"
-const SHORT = "{SHORTVER}"
+const Long = "{LONGVER}"
+const Short = "{SHORTVER}"
+const LONG = Long
+const SHORT = Short
+const GitCommit = "{GITCOMMIT}"
+const ExtraGitCommit = "{EXTRAGITCOMMIT}"

version/version.go

@@ -7,5 +7,35 @@
 // Package version provides the version that the binary was built at.
 package version
 
-const LONG = "date.20200921"
-const SHORT = LONG
+// Long is a full version number for this build, of the form
+// "x.y.z-commithash", or "date.yyyymmdd" if no actual version was
+// provided.
+const Long = "date.20200921"
+
+// Short is a short version number for this build, of the form
+// "x.y.z", or "date.yyyymmdd" if no actual version was provided.
+const Short = Long
+
+// LONG is a deprecated alias for Long. Don't use it.
+const LONG = Long
+
+// SHORT is a deprecated alias for Short. Don't use it.
+const SHORT = Short
+
+// GitCommit, if non-empty, is the git commit of the
+// github.com/tailscale/tailscale repository at which Tailscale was
+// built. Its format is the one returned by `git describe --always
+// --exclude "*" --dirty --abbrev=200`.
+const GitCommit = ""
+
+// ExtraGitCommit, if non-empty, is the git commit of a "supplemental"
+// repository at which Tailscale was built. Its format is the same as
+// GitRevision.
+//
+// ExtraGitRevision is used to track the source revision when the main
+// Tailscale repository is integrated into and built from another
+// repository (for example, Tailscale's proprietary code, or the
+// Android OSS repository). Together, GitRevision and ExtraGitRevision
+// exactly describe what repositories and commits were used in a
+// build.
+const ExtraGitCommit = ""

version/version.xcconfig.do

@@ -1,4 +1,5 @@
-redo-ifchange mkversion.sh describe.txt
+redo-ifchange mkversion.sh describe.txt extragitcommit.txt
 read -r describe <describe.txt
-ver=$(./mkversion.sh xcode "$describe")
+read -r other <extragitcommit.txt
+ver=$(./mkversion.sh xcode "$describe" "$other")
 echo "$ver" >$3

version/xversion.go

@@ -6,6 +6,12 @@
 
 package version
 
-// Replaced at build time with the Go linker flag -X.
-var LONG string = "<not set>"
-var SHORT string = "<not set>"
+// Replaced at build time with the Go linker flag -X. See
+// ../build_dist.sh for example usage, and version.go for field
+// documentation.
+var Long string = "<not set>"
+var Short string = "<not set>"
+var LONG = Long
+var SHORT = Short
+var GitCommit = ""
+var ExtraGitCommit = ""