Test with Go 1.19, upgrade golangci-lint (#35)

The previous version of the golangci-lint action would install its own
version of Go, which eventually conflicted with the old pinned version
of the linter I was using. Upgrade the action to avoid this, but also
update Go and the linter while I'm here.

.github/workflows/go.yml

···
     name: Verify
     runs-on: ubuntu-latest
     steps:
-      - name: Set up Go 1.16
-        uses: actions/setup-go@v2
+      - name: Set up Go 1.19
+        uses: actions/setup-go@v3
         with:
-          go-version: 1.16
+          go-version: 1.19
           
       - name: Check out code into the Go module directory
         uses: actions/checkout@v2
 
       - name: Lint
-        uses: golangci/golangci-lint-action@v2
+        uses: golangci/golangci-lint-action@v3
         with:
-          version: v1.28
+          version: v1.49
 
       - name: Test
         run: go test -v ./...

gitdiff/apply.go

···
 // Users can test if an error was caused by a conflict by using errors.Is with
 // an empty Conflict:
 //
-//     if errors.Is(err, &Conflict{}) {
-//	       // handle conflict
-//     }
-//
+//	    if errors.Is(err, &Conflict{}) {
+//		       // handle conflict
+//	    }
 type Conflict struct {
 	msg string
 }

gitdiff/apply_binary.go

···
 // readBinaryDeltaSize reads a variable length size from a delta-encoded binary
 // fragment, returing the size and the unused data. Data is encoded as:
 //
-//    [[1xxxxxxx]...] [0xxxxxxx]
+//	[[1xxxxxxx]...] [0xxxxxxx]
 //
 // in little-endian order, with 7 bits of the value per byte.
 func readBinaryDeltaSize(d []byte) (size int64, rest []byte) {
···
 // fragment, returning the amount of data written and the usused part of the
 // fragment. An add operation takes the form:
 //
-//     [0xxxxxx][[data1]...]
+//	[0xxxxxx][[data1]...]
 //
 // where the lower seven bits of the opcode is the number of data bytes
 // following the opcode. See also pack-format.txt in the Git source.
···
 // fragment, returing the amount of data written and the unused part of the
 // fragment. A copy operation takes the form:
 //
-//     [1xxxxxxx][offset1][offset2][offset3][offset4][size1][size2][size3]
+//	[1xxxxxxx][offset1][offset2][offset3][offset4][size1][size2][size3]
 //
 // where the lower seven bits of the opcode determine which non-zero offset and
 // size bytes are present in little-endian order: if bit 0 is set, offset1 is

gitdiff/apply_text.go

···
 //
 // By default, TextApplier operates in "strict" mode, where fragment content
 // and positions must exactly match those of the source.
-//
 type TextApplier struct {
 	dst      io.Writer
 	src      io.ReaderAt

gitdiff/testdata/apply/bin.go

···
-//+build ignore
+//go:build ignore
 
 // bin.go is a helper CLI to manipulate binary diff data for testing purposes.
 // It can decode patches generated by git using the standard parsing functions