Add Plan 9 support

Not all the tests pass yet but this makes go-git usable on Plan 9.
Please merge this after https://github.com/src-d/go-billy/pull/78.

Fixes #756

Signed-off-by: Fazlul Shahriar <fshahriar@gmail.com>

1 files changed, 47 insertions, 0 deletions

diff --git a/repository_plan9_test.go b/repository_plan9_test.go
new file mode 100644
index 0000000..00ebeed
--- /dev/null
+++ b/repository_plan9_test.go
@@ -0,0 +1,47 @@
+package git
+
+import (
+	"fmt"
+	"strings"
+)
+
+// preReceiveHook returns the bytes of a pre-receive hook script
+// that prints m before exiting successfully
+func preReceiveHook(m string) []byte {
+	return []byte(fmt.Sprintf("#!/bin/rc\necho -n %s\n", quote(m)))
+}
+
+const quoteChar = '\''
+
+func needsQuote(s string) bool {
+	for i := 0; i < len(s); i++ {
+		c := s[i]
+		if c == quoteChar || c <= ' ' { // quote, blanks, or control characters
+			return true
+		}
+	}
+	return false
+}
+
+// Quote adds single quotes to s in the style of rc(1) if they are needed.
+// The behaviour should be identical to Plan 9's quote(3).
+func quote(s string) string {
+	if s == "" {
+		return "''"
+	}
+	if !needsQuote(s) {
+		return s
+	}
+	var b strings.Builder
+	b.Grow(10 + len(s)) // Enough room for few quotes
+	b.WriteByte(quoteChar)
+	for i := 0; i < len(s); i++ {
+		c := s[i]
+		if c == quoteChar {
+			b.WriteByte(quoteChar)
+		}
+		b.WriteByte(c)
+	}
+	b.WriteByte(quoteChar)
+	return b.String()
+}