Fix support for Git copy status when status.renames=copies

Fixes #4890

When Git is configured with status.renames=copies, it can produce
status codes starting with "C" (copy) in addition to "R" (rename).
The file loader was only checking for "R" prefixes, causing copy
operations to be parsed incorrectly and breaking file staging.

This fix extends the status parser to handle both "R" and "C"
prefixes, ensuring proper support for Git's copy detection feature.

Fixes file staging issues when using status.renames=copies configuration.

pkg/commands/git_commands/file_loader.go

@@ -201,8 +201,8 @@ func (self *FileLoader) gitStatus(opts GitStatusOptions) ([]FileStatus, error) {
 			PreviousPath: "",
 		}
 
-		if strings.HasPrefix(status.Change, "R") {
-			// if a line starts with 'R' then the next line is the original file.
+		if strings.HasPrefix(status.Change, "R") || strings.HasPrefix(status.Change, "C") {
+			// if a line starts with 'R' (rename) or 'C' (copy) then the next line is the original file.
 			status.PreviousPath = splitLines[i+1]
 			status.StatusString = fmt.Sprintf("%s %s -> %s", status.Change, status.PreviousPath, status.Path)
 			i++

pkg/commands/git_commands/file_loader_test.go

@@ -192,6 +192,43 @@ func TestFileGetStatusFiles(t *testing.T) {
 				},
 			},
 		},
+		{
+			testName:            "Copied files",
+			similarityThreshold: 50,
+			runner: oscommands.NewFakeRunner(t).
+				ExpectGitArgs([]string{"status", "--untracked-files=yes", "--porcelain", "-z", "--find-renames=50%"},
+					"C  copy1.txt\x00original.txt\x00CM copy2.txt\x00original.txt",
+					nil,
+				),
+			expectedFiles: []*models.File{
+				{
+					Path:                    "copy1.txt",
+					PreviousPath:            "original.txt",
+					HasStagedChanges:        true,
+					HasUnstagedChanges:      false,
+					Tracked:                 true,
+					Added:                   false,
+					Deleted:                 false,
+					HasMergeConflicts:       false,
+					HasInlineMergeConflicts: false,
+					DisplayString:           "C  original.txt -> copy1.txt",
+					ShortStatus:             "C ",
+				},
+				{
+					Path:                    "copy2.txt",
+					PreviousPath:            "original.txt",
+					HasStagedChanges:        true,
+					HasUnstagedChanges:      true,
+					Tracked:                 true,
+					Added:                   false,
+					Deleted:                 false,
+					HasMergeConflicts:       false,
+					HasInlineMergeConflicts: false,
+					DisplayString:           "CM original.txt -> copy2.txt",
+					ShortStatus:             "CM",
+				},
+			},
+		},
 	}
 
 	for _, s := range scenarios {