fix: Pass /dev/null to diff command for missing files in apply --interactive

internal/chezmoi/externaldiffsystem.go

@@ -115,7 +115,7 @@ func (s *ExternalDiffSystem) Mkdir(name AbsPath, perm fs.FileMode) error {
 		if err := os.MkdirAll(targetAbsPath.String(), perm); err != nil {
 			return err
 		}
-		if err := s.RunDiffCommand(devNullAbsPath, targetAbsPath); err != nil {
+		if err := s.RunDiffCommand(DevNullAbsPath, targetAbsPath); err != nil {
 			return err
 		}
 	}
@@ -151,7 +151,7 @@ func (s *ExternalDiffSystem) Remove(name AbsPath) error {
 		case err != nil:
 			return err
 		case s.filter.IncludeFileInfo(fileInfo):
-			if err := s.RunDiffCommand(name, devNullAbsPath); err != nil {
+			if err := s.RunDiffCommand(name, DevNullAbsPath); err != nil {
 				return err
 			}
 		}
@@ -168,7 +168,7 @@ func (s *ExternalDiffSystem) RemoveAll(name AbsPath) error {
 		case err != nil:
 			return err
 		case s.filter.IncludeFileInfo(fileInfo):
-			if err := s.RunDiffCommand(name, devNullAbsPath); err != nil {
+			if err := s.RunDiffCommand(name, DevNullAbsPath); err != nil {
 				return err
 			}
 		}
@@ -304,7 +304,7 @@ func (s *ExternalDiffSystem) RunScript(scriptName RelPath, dir AbsPath, data []b
 		if err := os.WriteFile(targetAbsPath.String(), toData, 0o700); err != nil {
 			return err
 		}
-		if err := s.RunDiffCommand(devNullAbsPath, targetAbsPath); err != nil {
+		if err := s.RunDiffCommand(DevNullAbsPath, targetAbsPath); err != nil {
 			return err
 		}
 	}
@@ -340,7 +340,7 @@ func (s *ExternalDiffSystem) WriteFile(filename AbsPath, data []byte, perm fs.Fi
 		fromAbsPath := filename
 		switch fileInfo, err := os.Lstat(fromAbsPath.String()); {
 		case errors.Is(err, fs.ErrNotExist):
-			fromAbsPath = devNullAbsPath
+			fromAbsPath = DevNullAbsPath
 		case err != nil:
 			return err
 		case s.textConvFunc != nil:

internal/chezmoi/path_unix.go

@@ -7,7 +7,7 @@ import (
 	"strings"
 )
 
-var devNullAbsPath = NewAbsPath("/dev/null")
+var DevNullAbsPath = NewAbsPath("/dev/null")
 
 // NewAbsPathFromExtPath returns a new AbsPath by converting extPath to use
 // slashes, performing tilde expansion, and making the path absolute.

internal/chezmoi/path_windows.go

@@ -5,7 +5,7 @@ import (
 	"strings"
 )
 
-var devNullAbsPath = NewAbsPath("NUL:")
+var DevNullAbsPath = NewAbsPath("NUL:")
 
 // NewAbsPathFromExtPath returns a new AbsPath by converting extPath to use
 // slashes, performing tilde expansion, making the path absolute, and converting

internal/cmd/config.go

@@ -1197,9 +1197,13 @@ func (c *Config) defaultPreApplyFunc(
 		case err != nil:
 			return err
 		case choice == "diff":
+			destAbsPath := c.DestDirAbsPath.Join(targetRelPath)
+			if actualEntryState.Type == chezmoi.EntryStateTypeRemove {
+				destAbsPath = chezmoi.DevNullAbsPath
+			}
 			if err := c.diffFile(
 				targetRelPath,
-				c.DestDirAbsPath.Join(targetRelPath), actualContents, actualEntryState.Mode,
+				destAbsPath, actualContents, actualEntryState.Mode,
 				chezmoi.EmptyAbsPath, targetContents, targetEntryState.Mode,
 			); err != nil {
 				return err

internal/cmd/testdata/scripts/diffcommand_unix.txtar

@@ -1,5 +1,6 @@
 [windows] skip 'UNIX only'
 
+chmod 755 bin/diff-exists
 chmod 755 bin/diff-pager
 
 # test that chezmoi diff invokes diff.command when configured
@@ -59,10 +60,30 @@ cp golden/dot_file $CHEZMOISOURCEDIR
 exec chezmoi diff
 stdout diff-pager
 
+chhome home7/user
+
+stdin golden/diff-no
+exec chezmoi apply --interactive --no-tty
+stdout \s/dev/null\s+${WORK@R}/.*/\.file$
+! exists $HOME/.file
+
+-- bin/diff-exists --
+#!/bin/sh
+
+for arg in "$@"; do
+    if [ ! -e "$arg" ]; then
+        echo "$arg: no such file" >&2
+        exit 2
+    fi
+done
+echo "$@"
 -- bin/diff-pager --
 #!/bin/sh
 
 echo diff-pager
+-- golden/diff-no --
+diff
+no
 -- golden/diff-umask-002.diff --
 diff --git a/.file b/.file
 index bd729e8ee3cc005444c67dc77eed60016886b5e0..b508963510528ab709627ec448026a10a64c72ef 100664
@@ -118,3 +139,8 @@ index bd729e8ee3cc005444c67dc77eed60016886b5e0..b508963510528ab709627ec448026a10
 [diff]
     pager = "diff-pager"
 -- home6/user/.local/share/chezmoi/.keep --
+-- home7/user/.config/chezmoi/chezmoi.toml --
+[diff]
+    command = "diff-exists"
+-- home7/user/.local/share/chezmoi/dot_file --
+# contents of .file