diff3

Package diff3 implements a three-way merge algorithm Original version in Javascript by Bryan Housel @bhousel: https://github.com/bhousel/node-diff3, which in turn is based on project Synchrotron, created by Tony Garnock-Jones. For more detail please visit: http://homepages.kcbbs.gen.nz/tonyg/projects/synchrotron.html https://github.com/tonyg/synchrotron

Ported to go by Javier Peletier @jpeletier

How to use

Import the package and call Merge:

Merge(a, o, b io.Reader, detailed bool, labelA string, labelB string) (*MergeResult, error)

Where:

• a and b are the current and incoming versions of content
• o is the common ancestor
• detailed specifies whether you want the merge conflicts to be detailed.
• labelA and labelB indicate a label to mark conflicts with, usually the branch names.

Returns a MergeResult that includes a flag indicating whether there were conflicts or not and a io.Reader stream with the result.

For callers that already have line or token slices, call the generic API directly:

result := diff3.Diff3Merge(aLines, oLines, bLines, true)

The generic type parameter is inferred for common calls. If inference is not possible, specify it explicitly:

result := diff3.Diff3Merge[string](aLines, oLines, bLines, true)

Diff3Merge accepts any comparable element type, so callers can merge token slices as well as string lines.

Algorithm Selection

The default algorithm remains the original Hunt-McIlroy LCS implementation.

Use MergeWithOptions or Diff3MergeWithOptions to opt into Myers diff:

result, err := diff3.MergeWithOptions(a, o, b, diff3.MergeOptions{
	Algorithm:             diff3.DiffAlgorithmMyers,
	ExcludeFalseConflicts: true,
	Detailed:              true,
	LabelA:                "current",
	LabelB:                "incoming",
})

For slices:

result := diff3.Diff3MergeWithOptions(aLines, oLines, bLines, diff3.MergeOptions{
	Algorithm:             diff3.DiffAlgorithmMyers,
	ExcludeFalseConflicts: true,
})

Breaking API Changes

Diff3Merge, Diff3MergeResult, and Conflict are now generic.

Before:

var result []*diff3.Diff3MergeResult
var conflict *diff3.Conflict

After:

var result []*diff3.Diff3MergeResult[string]
var conflict *diff3.Conflict[string]

The fields on Diff3MergeResult and Conflict are now exported and inspectable:

for _, item := range result {
	if item.Ok != nil {
		// merged non-conflict block
	}

	if item.Conflict != nil {
		_ = item.Conflict.A
		_ = item.Conflict.O
		_ = item.Conflict.B
		_ = item.Conflict.AIndex
		_ = item.Conflict.OIndex
		_ = item.Conflict.BIndex
	}
}

Direct calls to Diff3Merge with []string usually continue to compile through type inference. Code that names Diff3MergeResult or Conflict must add the type argument, usually [string].

Attribution

The generic API, exported merge result fields, Myers diff implementation, and parallel diff computation are based on work by Kyungmin Bae and Devsisters in devsisters/go-diff3.