plumbing: format/gitattributes support

Implements gitattributes parsing, matching and attribute extraction.

Signed-off-by: Arran Walker <arran.walker@fiveturns.org>

1 files changed, 101 insertions, 0 deletions

diff --git a/plumbing/format/gitattributes/pattern.go b/plumbing/format/gitattributes/pattern.go
new file mode 100644
index 0000000..c5ca0c7
--- /dev/null
+++ b/plumbing/format/gitattributes/pattern.go
@@ -0,0 +1,101 @@
+package gitattributes
+
+import (
+	"path/filepath"
+	"strings"
+)
+
+const (
+	patternDirSep  = "/"
+	zeroToManyDirs = "**"
+)
+
+// Pattern defines a gitattributes pattern.
+type Pattern interface {
+	// Match matches the given path to the pattern.
+	Match(path []string) bool
+}
+
+type pattern struct {
+	domain  []string
+	pattern []string
+}
+
+// ParsePattern parses a gitattributes pattern string into the Pattern
+// structure.
+func ParsePattern(p string, domain []string) Pattern {
+	return &pattern{
+		domain:  domain,
+		pattern: strings.Split(p, patternDirSep),
+	}
+}
+
+func (p *pattern) Match(path []string) bool {
+	if len(path) <= len(p.domain) {
+		return false
+	}
+	for i, e := range p.domain {
+		if path[i] != e {
+			return false
+		}
+	}
+
+	if len(p.pattern) == 1 {
+		// for a simple rule, .gitattribute matching rules differs from
+		// .gitignore and only the last part of the path is considered.
+		path = path[len(path)-1:]
+	} else {
+		path = path[len(p.domain):]
+	}
+
+	pattern := p.pattern
+	var match, doublestar bool
+	var err error
+	for _, part := range path {
+		// skip empty
+		if pattern[0] == "" {
+			pattern = pattern[1:]
+		}
+
+		// eat doublestar
+		if pattern[0] == zeroToManyDirs {
+			pattern = pattern[1:]
+			if len(pattern) == 0 {
+				return true
+			}
+			doublestar = true
+		}
+
+		switch true {
+		case strings.Contains(pattern[0], "**"):
+			return false
+
+		// keep going down the path until we hit a match
+		case doublestar:
+			match, err = filepath.Match(pattern[0], part)
+			if err != nil {
+				return false
+			}
+
+			if match {
+				doublestar = false
+				pattern = pattern[1:]
+			}
+
+		default:
+			match, err = filepath.Match(pattern[0], part)
+			if err != nil {
+				return false
+			}
+			if !match {
+				return false
+			}
+			pattern = pattern[1:]
+		}
+	}
+
+	if len(pattern) > 0 {
+		return false
+	}
+	return match
+}