Implant version information with -ldflags with help of build script

Without -ldflags, the verison information needs to be updated manually,
which is never done between releases, so development builds appear
indiscernable from stable builds using `caddy -version`.

This is part of a set of changes intended to relieve the burden of
always updating version information manually and distributing binaries
that look stable but actually may not be.

A stable build is defined as one which is produced at a git tag with
a clean working directory (no uncommitted changes). A dev build is
anything else. With this build script, `caddy -version` will now reveal
whether it is a development build and, if so, the base version, the
latest commit, the date and time of build, and the names of files with
changes as well as how many changes were made.

The output of `caddy -version` for stable builds remains the same.

build.bash

+#!/usr/bin/env bash
+#
+# Caddy build script. Automates proper versioning.
+#
+# Usage:
+#
+#     $ ./build.bash [output_filename]
+#
+# Outputs compiled program in current directory.
+# Default file name is 'ecaddy'.
+#
+set -e
+
+output="$1"
+if [ -z "$output" ]; then
+	output="ecaddy"
+fi
+
+pkg=main
+
+# Timestamp of build
+builddate_id=$pkg.buildDate
+builddate=`date -u`
+
+# Current tag, if HEAD is on a tag
+tag_id=$pkg.gitTag
+set +e
+tag=`git describe --exact-match HEAD 2> /dev/null`
+set -e
+
+# Nearest tag on branch
+lasttag_id=$pkg.gitNearestTag
+lasttag=`git describe --abbrev=0 --tags HEAD`
+
+# Commit SHA
+commit_id=$pkg.gitCommit
+commit=`git rev-parse --short HEAD`
+
+# Summary of uncommited changes
+shortstat_id=$pkg.gitShortStat
+shortstat=`git diff-index --shortstat HEAD`
+
+# List of modified files
+files_id=$pkg.gitFilesModified
+files=`git diff-index --name-only HEAD`
+
+
+go build -ldflags "
+	-X \"$builddate_id=$builddate\"
+	-X \"$tag_id=$tag\"
+	-X \"$lasttag_id=$lasttag\"
+	-X \"$commit_id=$commit\"
+	-X \"$shortstat_id=$shortstat\"
+	-X \"$files_id=$files\"
+" -o "$output"

main.go

@@ -18,21 +18,9 @@ import (
 	"gopkg.in/natefinch/lumberjack.v2"
 )
 
-var (
-	conf    string
-	cpu     string
-	logfile string
-	revoke  string
-	version bool
-)
-
-const (
-	appName    = "Caddy"
-	appVersion = "0.8.2"
-)
-
 func init() {
 	caddy.TrapSignals()
+	setVersion()
 	flag.BoolVar(&https.Agreed, "agree", false, "Agree to Let's Encrypt Subscriber Agreement")
 	flag.StringVar(&https.CAUrl, "ca", "https://acme-v01.api.letsencrypt.org/directory", "Certificate authority ACME server")
 	flag.StringVar(&conf, "conf", "", "Configuration file to use (default="+caddy.DefaultConfigFile+")")
@@ -83,7 +71,10 @@ func main() {
 		os.Exit(0)
 	}
 	if version {
-		fmt.Printf("%s %s\n", caddy.AppName, caddy.AppVersion)
+		fmt.Printf("%s %s\n", appName, appVersion)
+		if devBuild && gitShortStat != "" {
+			fmt.Printf("%s\n%s\n", gitShortStat, gitFilesModified)
+		}
 		os.Exit(0)
 	}
 
@@ -199,3 +190,44 @@ func setCPU(cpu string) error {
 	runtime.GOMAXPROCS(numCPU)
 	return nil
 }
+
+// setVersion figures out the version information based on
+// variables set by -ldflags.
+func setVersion() {
+	// A development build is one that's not at a tag or has uncommitted changes
+	devBuild = gitTag == "" || gitShortStat != ""
+
+	// Only set the appVersion if -ldflags was used
+	if gitNearestTag != "" || gitTag != "" {
+		if devBuild && gitNearestTag != "" {
+			appVersion = fmt.Sprintf("%s (+%s %s)",
+				strings.TrimPrefix(gitNearestTag, "v"), gitCommit, buildDate)
+		} else if gitTag != "" {
+			appVersion = strings.TrimPrefix(gitTag, "v")
+		}
+	}
+}
+
+const appName = "Caddy"
+
+// Flags that control program flow or startup
+var (
+	conf    string
+	cpu     string
+	logfile string
+	revoke  string
+	version bool
+)
+
+// Build information obtained with the help of -ldflags
+var (
+	appVersion = "(untracked dev build)" // inferred at startup
+	devBuild   = true                    // inferred at startup
+
+	buildDate        string // date -u
+	gitTag           string // git describe --exact-match HEAD 2> /dev/null
+	gitNearestTag    string // git describe --abbrev=0 --tags HEAD
+	gitCommit        string // git rev-parse HEAD
+	gitShortStat     string // git diff-index --shortstat
+	gitFilesModified string // git diff-index --name-only HEAD
+)

main_test.go

@@ -42,3 +42,34 @@ func TestSetCPU(t *testing.T) {
 		runtime.GOMAXPROCS(currentCPU)
 	}
 }
+
+func TestSetVersion(t *testing.T) {
+	setVersion()
+	if !devBuild {
+		t.Error("Expected default to assume development build, but it didn't")
+	}
+	if got, want := appVersion, "(untracked dev build)"; got != want {
+		t.Errorf("Expected appVersion='%s', got: '%s'", want, got)
+	}
+
+	gitTag = "v1.1"
+	setVersion()
+	if devBuild {
+		t.Error("Expected a stable build if gitTag is set with no changes")
+	}
+	if got, want := appVersion, "1.1"; got != want {
+		t.Errorf("Expected appVersion='%s', got: '%s'", want, got)
+	}
+
+	gitTag = ""
+	gitNearestTag = "v1.0"
+	gitCommit = "deadbeef"
+	buildDate = "Fri Feb 26 06:53:17 UTC 2016"
+	setVersion()
+	if !devBuild {
+		t.Error("Expected inferring a dev build when gitTag is empty")
+	}
+	if got, want := appVersion, "1.0 (+deadbeef Fri Feb 26 06:53:17 UTC 2016)"; got != want {
+		t.Errorf("Expected appVersion='%s', got: '%s'", want, got)
+	}
+}