Fix breaking changes count (#48)

* Accurately count the number of breaking changes

We previously related the number of breaking changes with the number of breaking changes
printed (which was capped at 500). By abstracting the printing mechanism to understand its
own capacity, we get an accurate count of the number of conflicts without increasing code
complexity in the display mechanism.

* Add a `make install` target

* Nit: max -> remaining

Author: iwahbe

Makefile

@@ -1,11 +1,14 @@
-VERSION=$(shell git describe --tags)
+VERSION:=$(shell git describe --tags)
+LDFLAGS=-ldflags="-X github.com/pulumi/schema-tools/version.Version=$(VERSION)"
 
 test:
 	go test ./...
 
 build:
-	go build \
-		-ldflags="-X github.com/pulumi/schema-tools/version.Version=$(VERSION)"
+	go build $(LDFLAGS)
 
 lint:
 	golangci-lint run
+
+install:
+	go install $(LDFLAGS)

internal/util/diagtree/diagtree.go

@@ -70,16 +70,37 @@ func (m *Node) levelPrefix(level int) string {
 	return strings.Repeat("  ", (level-2)*2) + "- "
 }
 
+type cappedWriter struct {
+	// The number of remaining writes before we hit the cap.
+	remaining int
+	out       io.Writer
+}
+
+func (c *cappedWriter) incr() {
+	if c.remaining > 0 {
+		c.remaining--
+	}
+}
+
+func (c *cappedWriter) Write(p []byte) (n int, err error) {
+	if c.remaining > 0 {
+		return c.out.Write(p)
+	}
+	// We pretend we finished the write, but we do nothing.
+	return len(p), nil
+}
+
 func (m *Node) Display(out io.Writer, max int) int {
-	return m.display(out, 0, true, max)
+	writer := &cappedWriter{max, out}
+	return m.display(writer, 0, true)
 }
 
-func (m *Node) display(out io.Writer, level int, prefix bool, max int) int {
+func (m *Node) display(out *cappedWriter, level int, prefix bool) int {
 	write := func(s string) {
 		_, err := out.Write([]byte(s))
 		contract.AssertNoErrorf(err, "failed to write display")
 	}
-	if m == nil || !m.doDisplay || max <= 0 {
+	if m == nil || !m.doDisplay {
 		// Nothing to display
 		return 0
 	}
@@ -102,12 +123,13 @@ func (m *Node) display(out io.Writer, level int, prefix bool, max int) int {
 		}
 
 		write(display)
+		out.incr()
 	}
 
 	if level > 1 && m.Severity == None {
 		if s := m.uniqueSuccessor(); s != nil {
 			write(": ")
-			return s.display(out, level, false, max-displayed) + displayed
+			return s.display(out, level, false) + displayed
 		}
 	}
 
@@ -132,7 +154,7 @@ func (m *Node) display(out io.Writer, level int, prefix bool, max int) int {
 			}
 			didEndLine = true
 		}
-		n := m.subfields[i].display(out, level+1, true, max-displayed)
+		n := m.subfields[i].display(out, level+1, true)
 		displayed += n
 	}