From 67267aa9aebbd56342e02c5c0d3ed295c15be867 Mon Sep 17 00:00:00 2001
From: Evan Purkhiser <evanpurkhiser@gmail.com>
Date: Tue, 24 Jul 2018 00:32:12 -0700
Subject: [PATCH] Improve handing of mode / permissions on install

---
 installer/installer.go | 13 ++++++++-----
 installer/prepare.go   | 35 +++++++++++++++++++++--------------
 2 files changed, 29 insertions(+), 19 deletions(-)

diff --git a/installer/installer.go b/installer/installer.go
index e205e5d..21dca11 100644
--- a/installer/installer.go
+++ b/installer/installer.go
@@ -36,8 +36,7 @@ func InstallDotfile(dotfile *PreparedDotfile, config InstallConfig) error {
 		return fmt.Errorf("Source files are not all regular files")
 	}
 
-	// No change
-	if !dotfile.IsNew && !dotfile.ContentsDiffer && dotfile.Permissions.IsSame() {
+	if !dotfile.IsChanged() {
 		return nil
 	}
 
@@ -46,10 +45,14 @@ func InstallDotfile(dotfile *PreparedDotfile, config InstallConfig) error {
 		return os.Remove(installPath)
 	}
 
-	targetMode := dotfile.Permissions.New | dotfile.Mode
+	targetMode := dotfile.Permissions.New | dotfile.Mode.New
 
-	// Only permissions differ
-	if !dotfile.IsNew && !dotfile.Permissions.IsSame() && !dotfile.ContentsDiffer {
+	// Only filemode differs
+	modeChanged := !dotfile.IsNew &&
+		!dotfile.ContentsDiffer &&
+		(dotfile.Permissions.IsChanged() || dotfile.Mode.IsChanged())
+
+	if modeChanged {
 		return os.Chmod(installPath, targetMode)
 	}
 
diff --git a/installer/prepare.go b/installer/prepare.go
index 9234b96..bdaac68 100644
--- a/installer/prepare.go
+++ b/installer/prepare.go
@@ -26,14 +26,15 @@ type PreparedDotfile struct {
 	// compiled or installed.
 	SourcesAreIrregular bool
 
-	// Mode represents the mode bits of the os.FileMode (does not include
-	// permissions). This will not be set if the sources are irregular.
-	Mode os.FileMode
+	// Mode represents the change in the file mode bits of the source and
+	// target os.FileMode (does not include permissions). This will not be set
+	// if the sources are irregular.
+	Mode *FileMode
 
 	// Permissions represents the change in permission between the compiled source
 	// and the currently installed dotfile. Equal permissions can be verified
 	// by calling Permissions.IsSame.
-	Permissions Permissions
+	Permissions *FileMode
 
 	// SourcePermissionsDiffer indicates that a compiled dotfile (one with
 	// multiple sources) does not have consistent permissions across all
@@ -55,15 +56,21 @@ type PreparedDotfile struct {
 	sourceInfo []os.FileInfo
 }
 
-// Permissions represents a change in file permissions.
-type Permissions struct {
+// IsChanged reports if the prepared dotfile has changes from the target
+// dotfile.
+func (p *PreparedDotfile) IsChanged() bool {
+	return p.IsNew || p.ContentsDiffer || p.Permissions.IsChanged() || p.Mode.IsChanged()
+}
+
+// FileMode represents the new and old dotfile file mode.
+type FileMode struct {
 	Old os.FileMode
 	New os.FileMode
 }
 
-// IsSame returns a boolean value indicating if the modes are equal.
-func (d Permissions) IsSame() bool {
-	return d.New == d.Old
+// IsChanged returns a boolean value indicating if the modes are equal.
+func (d FileMode) IsChanged() bool {
+	return d.New != d.Old
 }
 
 // PreparedDotfiles is a list of prepared dotfiles.
@@ -129,7 +136,7 @@ func PrepareDotfiles(dotfiles resolver.Dotfiles, config config.SourceConfig) Pre
 
 		sourcePermissions, tookLowest := flattenPermissions(sourceInfo)
 
-		prepared.Permissions = Permissions{
+		prepared.Permissions = &FileMode{
 			Old: targetInfo.Mode() & os.ModePerm,
 			New: sourcePermissions,
 		}
@@ -137,11 +144,11 @@ func PrepareDotfiles(dotfiles resolver.Dotfiles, config config.SourceConfig) Pre
 
 		prepared.SourcesAreIrregular = !isAllRegular(sourceInfo)
 
-		// NOTE: This currently drops non-mode bits (permissions are included
-		// seperately), however should the dotfile set ModeAppend, ModeSticky,
-		// etc, these modes will not be included here.
 		if !prepared.SourcesAreIrregular {
-			prepared.Mode = sourceInfo[0].Mode() & os.ModeType
+			prepared.Mode = &FileMode{
+				Old: targetInfo.Mode() &^ os.ModePerm,
+				New: sourceInfo[0].Mode() &^ os.ModePerm,
+			}
 		}
 
 		// If the dotfile does not require compilation we can directly compare