feat: add support for rendering .Body after .Subject as part of list (#121)

When attempting to render a commit body below the summary line of the
commit there are two problems:

1) The text needs to be indented two spaces to appear as part of the
list.

2) Notes (e.g. BREAKING CHANGE) are included in the body and end up
being repeating in a Notes section (if this is part of your template).

To address #1 add an `indent` func to the template parsing.
To address #2 add a `TrimmedBody` to the `Commit` fields.

The `TrimmedBody` will include everything in `Body` but not any
`Ref`s, `Note`s, `Mention`s, `CoAuthors`, or `Signers`.

Both the CoAuthors and Signers are now first class in the Commit
struct.

With both of these a template block like:

```
{{ if .TrimmedBody -}}
{{ indent .TrimmedBody 2 }}
{{ end -}}
```

Will render the trimmed down body section as intended.

See TestGeneratorWithTimmedBody for example of desired output.

commit_parser.go

@@ -59,6 +59,8 @@ type commitParser struct {
 	reIssue                *regexp.Regexp
 	reNotes                *regexp.Regexp
 	reMention              *regexp.Regexp
+	reSignOff              *regexp.Regexp
+	reCoAuthor             *regexp.Regexp
 	reJiraIssueDescription *regexp.Regexp
 }
 
@@ -81,6 +83,8 @@ func newCommitParser(logger *Logger, client gitcmd.Client, jiraClient JiraClient
 		reIssue:                regexp.MustCompile("(?:" + joinedIssuePrefix + ")(\\d+)"),
 		reNotes:                regexp.MustCompile("^(?i)\\s*(" + joinedNoteKeywords + ")[:\\s]+(.*)"),
 		reMention:              regexp.MustCompile(`@([\w-]+)`),
+		reSignOff:              regexp.MustCompile(`Signed-off-by:\s+([\p{L}\s\-\[\]]+)\s+<([\w+\-\[\].@]+)>`),
+		reCoAuthor:             regexp.MustCompile(`Co-authored-by:\s+([\p{L}\s\-\[\]]+)\s+<([\w+\-\[\].@]+)>`),
 		reJiraIssueDescription: regexp.MustCompile(opts.JiraIssueDescriptionPattern),
 	}
 }
@@ -228,6 +232,36 @@ func (p *commitParser) processHeader(commit *Commit, input string) {
 	}
 }
 
+func (p *commitParser) extractLineMetadata(commit *Commit, line string) bool {
+	meta := false
+
+	refs := p.parseRefs(line)
+	if len(refs) > 0 {
+		meta = true
+		commit.Refs = append(commit.Refs, refs...)
+	}
+
+	mentions := p.parseMentions(line)
+	if len(mentions) > 0 {
+		meta = true
+		commit.Mentions = append(commit.Mentions, mentions...)
+	}
+
+	coAuthors := p.parseCoAuthors(line)
+	if len(coAuthors) > 0 {
+		meta = true
+		commit.CoAuthors = append(commit.CoAuthors, coAuthors...)
+	}
+
+	signers := p.parseSigners(line)
+	if len(signers) > 0 {
+		meta = true
+		commit.Signers = append(commit.Signers, signers...)
+	}
+
+	return meta
+}
+
 func (p *commitParser) processBody(commit *Commit, input string) {
 	input = convNewline(input, "\n")
 
@@ -237,30 +271,29 @@ func (p *commitParser) processBody(commit *Commit, input string) {
 	// notes & refs & mentions
 	commit.Notes = []*Note{}
 	inNote := false
+	trim := false
 	fenceDetector := newMdFenceDetector()
 	lines := strings.Split(input, "\n")
 
+	// body without notes & refs & mentions
+	trimmedBody := make([]string, 0, len(lines))
+
 	for _, line := range lines {
+		if !inNote {
+			trim = false
+		}
 		fenceDetector.Update(line)
 
-		if !fenceDetector.InCodeblock() {
-			refs := p.parseRefs(line)
-			if len(refs) > 0 {
-				inNote = false
-				commit.Refs = append(commit.Refs, refs...)
-			}
-
-			mentions := p.parseMentions(line)
-			if len(mentions) > 0 {
-				inNote = false
-				commit.Mentions = append(commit.Mentions, mentions...)
-			}
+		if !fenceDetector.InCodeblock() && p.extractLineMetadata(commit, line) {
+			trim = true
+			inNote = false
 		}
-
+		// Q: should this check also only be outside of code blocks?
 		res := p.reNotes.FindAllStringSubmatch(line, -1)
 
 		if len(res) > 0 {
 			inNote = true
+			trim = true
 			for _, r := range res {
 				commit.Notes = append(commit.Notes, &Note{
 					Title: r[1],
@@ -271,8 +304,13 @@ func (p *commitParser) processBody(commit *Commit, input string) {
 			last := commit.Notes[len(commit.Notes)-1]
 			last.Body = last.Body + "\n" + line
 		}
+
+		if !trim {
+			trimmedBody = append(trimmedBody, line)
+		}
 	}
 
+	commit.TrimmedBody = strings.TrimSpace(strings.Join(trimmedBody, "\n"))
 	p.trimSpaceInNotes(commit)
 }
 
@@ -317,6 +355,30 @@ func (p *commitParser) parseRefs(input string) []*Ref {
 	return refs
 }
 
+func (p *commitParser) parseSigners(input string) []Contact {
+	res := p.reSignOff.FindAllStringSubmatch(input, -1)
+	contacts := make([]Contact, len(res))
+
+	for i, r := range res {
+		contacts[i].Name = r[1]
+		contacts[i].Email = r[2]
+	}
+
+	return contacts
+}
+
+func (p *commitParser) parseCoAuthors(input string) []Contact {
+	res := p.reCoAuthor.FindAllStringSubmatch(input, -1)
+	contacts := make([]Contact, len(res))
+
+	for i, r := range res {
+		contacts[i].Name = r[1]
+		contacts[i].Email = r[2]
+	}
+
+	return contacts
+}
+
 func (p *commitParser) parseMentions(input string) []string {
 	res := p.reMention.FindAllStringSubmatch(input, -1)
 	mentions := make([]string, len(res))