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Go
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import ( "fmt" "strings"
"github.com/bluekeyes/go-gitdiff/gitdiff")
// original1 -> patch1 -> rev1// original2 -> patch2 -> rev2//// original2 must be equal to rev1, so we can merge them to get maximal context//// finally,// rev2' <- apply(patch2, merged)// combineddiff <- diff(rev2', original1)func combineFiles(file1, file2 *gitdiff.File) (*gitdiff.File, error) { fileName := bestName(file1)
o1 := CreatePreImage(file1) r1 := CreatePostImage(file1) o2 := CreatePreImage(file2)
merged, err := r1.Merge(&o2) if err != nil { return nil, err }
r2Prime, err := merged.Apply(file2) if err != nil { return nil, err }
// produce combined diff diff, err := Unified(o1.String(), fileName, r2Prime, fileName) if err != nil { return nil, err }
parsed, _, err := gitdiff.Parse(strings.NewReader(diff))
if len(parsed) != 1 { // no diff? the second commit reverted the changes from the first return nil, nil }
return parsed[0], nil}
// use empty lines for lines we are unaware of//// this raises an error only if the two patches were invalid or non-contiguousfunc mergeLines(old, new string) (string, error) { var i, j int
// TODO: use strings.Lines linesOld := strings.Split(old, "\n") linesNew := strings.Split(new, "\n")
result := []string{}
for i < len(linesOld) || j < len(linesNew) { if i >= len(linesOld) { // rest of the file is populated from `new` result = append(result, linesNew[j]) j++ continue }
if j >= len(linesNew) { // rest of the file is populated from `old` result = append(result, linesOld[i]) i++ continue }
oldLine := linesOld[i] newLine := linesNew[j]
if oldLine != newLine && (oldLine != "" && newLine != "") { // context mismatch return "", fmt.Errorf("failed to merge files, found context mismatch at %d; oldLine: `%s`, newline: `%s`", i+1, oldLine, newLine) }
if oldLine == newLine { result = append(result, oldLine) } else if oldLine == "" { result = append(result, newLine) } else if newLine == "" { result = append(result, oldLine) } i++ j++ }
return strings.Join(result, "\n"), nil}
func combineTwo(patch1, patch2 []*gitdiff.File) []*gitdiff.File { fileToIdx1 := make(map[string]int) fileToIdx2 := make(map[string]int) visited := make(map[string]struct{}) var result []*gitdiff.File
for idx, f := range patch1 { fileToIdx1[bestName(f)] = idx }
for idx, f := range patch2 { fileToIdx2[bestName(f)] = idx }
for _, f1 := range patch1 { fileName := bestName(f1) if idx, ok := fileToIdx2[fileName]; ok { f2 := patch2[idx]
// we have f1 and f2, combine them combined, err := combineFiles(f1, f2) if err != nil { // fmt.Println(err) }
// combined can be nil commit 2 reverted all changes from commit 1 if combined != nil { result = append(result, combined) }
} else { // only in patch1; add as-is result = append(result, f1) }
visited[fileName] = struct{}{} }
// for all files in patch2 that remain unvisited; we can just add them into the output for _, f2 := range patch2 { fileName := bestName(f2) if _, ok := visited[fileName]; ok { continue }
result = append(result, f2) }
return result}
// pairwise combination from first to last patchfunc CombineDiff(patches ...[]*gitdiff.File) []*gitdiff.File { if len(patches) == 0 { return nil }
if len(patches) == 1 { return patches[0] }
combined := combineTwo(patches[0], patches[1])
newPatches := [][]*gitdiff.File{} newPatches = append(newPatches, combined) for i, p := range patches { if i >= 2 { newPatches = append(newPatches, p) } }
return CombineDiff(newPatches...)}