[minor] use osext module to find agent executable path

Makefile

@@ -68,6 +68,7 @@ go_get_deps:
 	$(GOGETTER) github.com/VividCortex/godaemon
 	$(GOGETTER) github.com/gorilla/mux
 	$(GOGETTER) github.com/jvehent/cljs
+	$(GOGETTER) bitbucket.org/kardianos/osext
 
 install: gpgme mig-agent mig-scheduler
 	$(INSTALL) -D -m 0755 $(BINDIR)/mig-agent $(DESTDIR)$(PREFIX)/sbin/mig-agent

src/mig/agent/context.go

@@ -36,6 +36,7 @@ the terms of any one of the MPL, the GPL or the LGPL.
 package main
 
 import (
+	"bitbucket.org/kardianos/osext"
 	"crypto/rand"
 	"crypto/tls"
 	"crypto/x509"
@@ -95,18 +96,10 @@ func Init(foreground bool) (ctx Context, err error) {
 		ctx.Channels.Log <- mig.Log{Desc: "leaving initAgent()"}.Debug()
 	}()
 
-	// find out current working dir and build the bin path
-	// it's important to do that before we daemonize, other the cwd will be /
-	cdir := ""
-	char := fmt.Sprintf("%c", os.Args[0][0])
-	if char == "." {
-		// command start with a dot, prepend the current dir
-		cdir, err = os.Getwd()
-		if err != nil {
-			panic(err)
-		}
+	ctx.Agent.BinPath, err = osext.Executable()
+	if err != nil {
+		panic(err)
 	}
-	ctx.Agent.BinPath = cdir + "/" + os.Args[0]
 
 	// daemonize, and force logging to stdout
 	if !foreground && LOGGINGCONF.Mode != "stdout" {