Render the git graph on the server (#12333)

Rendering the git graph on the server means that we can properly track flows and switch from the Canvas implementation to a SVG implementation.

* This implementation provides a 16 limited color selection
* The uniqued color numbers are also provided
* And there is also a monochrome version
*In addition is a hover highlight that allows users to highlight commits on the same flow.

Closes #12209

Signed-off-by: Andrew Thornton art27@cantab.net
Co-authored-by: silverwind <me@silverwind.io>

modules/gitgraph/graph_models.go

@@ -0,0 +1,186 @@
+// Copyright 2020 The Gitea Authors. All rights reserved.
+// Use of this source code is governed by a MIT-style
+// license that can be found in the LICENSE file.
+
+package gitgraph
+
+import (
+	"bytes"
+	"fmt"
+)
+
+// NewGraph creates a basic graph
+func NewGraph() *Graph {
+	graph := &Graph{}
+	graph.relationCommit = &Commit{
+		Row:    -1,
+		Column: -1,
+	}
+	graph.Flows = map[int64]*Flow{}
+	return graph
+}
+
+// Graph represents a collection of flows
+type Graph struct {
+	Flows          map[int64]*Flow
+	Commits        []*Commit
+	MinRow         int
+	MinColumn      int
+	MaxRow         int
+	MaxColumn      int
+	relationCommit *Commit
+}
+
+// Width returns the width of the graph
+func (graph *Graph) Width() int {
+	return graph.MaxColumn - graph.MinColumn + 1
+}
+
+// Height returns the height of the graph
+func (graph *Graph) Height() int {
+	return graph.MaxRow - graph.MinRow + 1
+}
+
+// AddGlyph adds glyph to flows
+func (graph *Graph) AddGlyph(row, column int, flowID int64, color int, glyph byte) {
+	flow, ok := graph.Flows[flowID]
+	if !ok {
+		flow = NewFlow(flowID, color, row, column)
+		graph.Flows[flowID] = flow
+	}
+	flow.AddGlyph(row, column, glyph)
+
+	if row < graph.MinRow {
+		graph.MinRow = row
+	}
+	if row > graph.MaxRow {
+		graph.MaxRow = row
+	}
+	if column < graph.MinColumn {
+		graph.MinColumn = column
+	}
+	if column > graph.MaxColumn {
+		graph.MaxColumn = column
+	}
+}
+
+// AddCommit adds a commit at row, column on flowID with the provided data
+func (graph *Graph) AddCommit(row, column int, flowID int64, data []byte) error {
+	commit, err := NewCommit(row, column, data)
+	if err != nil {
+		return err
+	}
+	commit.Flow = flowID
+	graph.Commits = append(graph.Commits, commit)
+
+	graph.Flows[flowID].Commits = append(graph.Flows[flowID].Commits, commit)
+	return nil
+}
+
+// NewFlow creates a new flow
+func NewFlow(flowID int64, color, row, column int) *Flow {
+	return &Flow{
+		ID:          flowID,
+		ColorNumber: color,
+		MinRow:      row,
+		MinColumn:   column,
+		MaxRow:      row,
+		MaxColumn:   column,
+	}
+}
+
+// Flow represents a series of glyphs
+type Flow struct {
+	ID          int64
+	ColorNumber int
+	Glyphs      []Glyph
+	Commits     []*Commit
+	MinRow      int
+	MinColumn   int
+	MaxRow      int
+	MaxColumn   int
+}
+
+// Color16 wraps the color numbers around mod 16
+func (flow *Flow) Color16() int {
+	return flow.ColorNumber % 16
+}
+
+// AddGlyph adds glyph at row and column
+func (flow *Flow) AddGlyph(row, column int, glyph byte) {
+	if row < flow.MinRow {
+		flow.MinRow = row
+	}
+	if row > flow.MaxRow {
+		flow.MaxRow = row
+	}
+	if column < flow.MinColumn {
+		flow.MinColumn = column
+	}
+	if column > flow.MaxColumn {
+		flow.MaxColumn = column
+	}
+
+	flow.Glyphs = append(flow.Glyphs, Glyph{
+		row,
+		column,
+		glyph,
+	})
+}
+
+// Glyph represents a co-ordinate and glyph
+type Glyph struct {
+	Row    int
+	Column int
+	Glyph  byte
+}
+
+// RelationCommit represents an empty relation commit
+var RelationCommit = &Commit{
+	Row: -1,
+}
+
+// NewCommit creates a new commit from a provided line
+func NewCommit(row, column int, line []byte) (*Commit, error) {
+	data := bytes.SplitN(line, []byte("|"), 7)
+	if len(data) < 7 {
+		return nil, fmt.Errorf("malformed data section on line %d with commit: %s", row, string(line))
+	}
+	return &Commit{
+		Row:    row,
+		Column: column,
+		// 0 matches git log --pretty=format:%d => ref names, like the --decorate option of git-log(1)
+		Branch: string(data[0]),
+		// 1 matches git log --pretty=format:%H => commit hash
+		Rev: string(data[1]),
+		// 2 matches git log --pretty=format:%ad => author date (format respects --date= option)
+		Date: string(data[2]),
+		// 3 matches git log --pretty=format:%an => author name
+		Author: string(data[3]),
+		// 4 matches git log --pretty=format:%ae => author email
+		AuthorEmail: string(data[4]),
+		// 5 matches git log --pretty=format:%h => abbreviated commit hash
+		ShortRev: string(data[5]),
+		// 6 matches git log --pretty=format:%s => subject
+		Subject: string(data[6]),
+	}, nil
+}
+
+// Commit represents a commit at co-ordinate X, Y with the data
+type Commit struct {
+	Flow        int64
+	Row         int
+	Column      int
+	Branch      string
+	Rev         string
+	Date        string
+	Author      string
+	AuthorEmail string
+	ShortRev    string
+	Subject     string
+}
+
+// OnlyRelation returns whether this a relation only commit
+func (c *Commit) OnlyRelation() bool {
+	return c.Row == -1
+}