replace invalid TMPDIR variable wth PACKER_TMP_DIR.

update ConfigTmpDir() to try common temporary paths first and
only write to configDir() as a last resort.

packer/config_file.go

@@ -20,17 +20,24 @@ func ConfigDir() (string, error) {
 
 // ConfigTmpDir returns the configuration tmp directory for Packer
 func ConfigTmpDir() (string, error) {
-	if tmpdir := os.Getenv("PACKER_TMP_DIR"); tmpdir != "" {
-		return filepath.Abs(tmpdir)
+	var tmpdir, td string
+	var found bool
+
+	if tmpdir = os.Getenv("PACKER_TMP_DIR"); tmpdir == "" {
+		for e := range []string{"TEMP", "TMP", "LOCALAPPDATA"} {
+			if tmpdir, found := os.LookupEnv(e); found {
+				td = filepath.Join(tmpdir, "packer")
+				break
+			}
+		}
 	}
-	configdir, err := configDir()
-	if err != nil {
-		return "", err
+	if tmpdir == "" {
+		td = filepath.Join(configDir(), "tmp")
 	}
-	td := filepath.Join(configdir, "tmp")
+
 	_, err = os.Stat(td)
 	if os.IsNotExist(err) {
-		if err = os.MkdirAll(td, 0755); err != nil {
+		if err = os.MkdirAll(td, 0700); err != nil {
 			return "", err
 		}
 	} else if err != nil {

packer/config_file_unix.go

@@ -18,7 +18,7 @@ func configFile() (string, error) {
 		return "", err
 	}
 
-	return filepath.Join(dir, ".packerconfig"), nil
+	return filepath.Join(dir, "packer.config"), nil
 }
 
 func configDir() (string, error) {

website/source/docs/other/debugging.html.md

@@ -139,4 +139,4 @@ Failed to initialize build 'docker': error initializing builder 'docker': plugin
 ```
 
 you should try setting your temp directory to something shorter. This can be
-done through the `TMPDIR` environment variable.
+done through the `PACKER_TMP_DIR` environment variable.

website/source/docs/other/environment-variables.html.md

@@ -42,9 +42,10 @@ each can be found below:
     new versions of Packer. If you want to disable this for security or privacy
     reasons, you can set this environment variable to `1`.
 
--   `TMPDIR` (Unix) / `TMP` (Windows) - The location of the directory used for
-    temporary files (defaults to `/tmp` on Linux/Unix and
-    `%USERPROFILE%\AppData\Local\Temp` on Windows Vista and above). It might be
-    necessary to customize it when working with large files since `/tmp` is a
-    memory-backed filesystem in some Linux distributions in which case
-    `/var/tmp` might be preferred.
+-   `PACKER_TMP_DIR` - The directory used for temporary files during marshalling.
+    If unset, appends 'packer' to environment variables TEMP, TMP, or LOCALAPPDATA 
+    (Windows) before falling back to the value of `configDir()/tmp` which resolves
+    to `$HOME/.packer.d/` (Unix) or `%APPDAT%\packer.d` (Windows).
+    This is not to be confused with the provisionee's temporary directory which
+    is often defined (hard-coded) as '/tmp' or '%SYSTEMROOT%\Temp' per each 
+    provisioner module.