internal/upload: Add support for upload to GCP and CLI tool using it

Add new internal upload target for Google Cloud Platform and
osbuild-upload-gcp CLI tool which uses the API.

Supported features are:
- Authenticate with GCP using explicitly provided JSON credentials
  file or let the authentication be handled automatically by the
  Google cloud client library. The later is useful e.g. when the worker
  is running in GCP VM instance, which has associated permissions with
  it.
- Upload an existing image file into existing Storage bucket.
- Verify MD5 checksum of the uploaded image file against the local
  file's checksum.
- Import the uploaded image file into Compute Node as an Image.
- Delete the uploaded image file after a successful image import.
- Delete all cache files from storage created as part of the image
  import build job.
- Share the imported image with a list of specified accounts.

GCP-specific image type is not yet added, since GCP supports importing
VMDK and VHD images, which the osbuild-composer already supports.

Update go.mod, vendor/ content and SPEC file with new dependencies.

Signed-off-by: Tomas Hozza <thozza@redhat.com>

vendor/github.com/google/go-cmp/cmp/path.go

@@ -1,6 +1,6 @@
 // Copyright 2017, The Go Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE.md file.
+// license that can be found in the LICENSE file.
 
 package cmp
 
@@ -10,6 +10,8 @@ import (
 	"strings"
 	"unicode"
 	"unicode/utf8"
+
+	"github.com/google/go-cmp/cmp/internal/value"
 )
 
 // Path is a list of PathSteps describing the sequence of operations to get
@@ -41,7 +43,7 @@ type PathStep interface {
 	// In some cases, one or both may be invalid or have restrictions:
 	//	• For StructField, both are not interface-able if the current field
 	//	is unexported and the struct type is not explicitly permitted by
-	//	AllowUnexported to traverse unexported fields.
+	//	an Exporter to traverse unexported fields.
 	//	• For SliceIndex, one may be invalid if an element is missing from
 	//	either the x or y slice.
 	//	• For MapIndex, one may be invalid if an entry is missing from
@@ -175,7 +177,8 @@ type structField struct {
 	// pvx, pvy, and field are only valid if unexported is true.
 	unexported bool
 	mayForce   bool                // Forcibly allow visibility
-	pvx, pvy   reflect.Value       // Parent values
+	paddr      bool                // Was parent addressable?
+	pvx, pvy   reflect.Value       // Parent values (always addressible)
 	field      reflect.StructField // Field information
 }
 
@@ -187,8 +190,8 @@ func (sf StructField) Values() (vx, vy reflect.Value) {
 
 	// Forcibly obtain read-write access to an unexported struct field.
 	if sf.mayForce {
-		vx = retrieveUnexportedField(sf.pvx, sf.field)
-		vy = retrieveUnexportedField(sf.pvy, sf.field)
+		vx = retrieveUnexportedField(sf.pvx, sf.field, sf.paddr)
+		vy = retrieveUnexportedField(sf.pvy, sf.field, sf.paddr)
 		return vx, vy // CanInterface reports true
 	}
 	return sf.vx, sf.vy // CanInterface reports false
@@ -207,6 +210,7 @@ type SliceIndex struct{ *sliceIndex }
 type sliceIndex struct {
 	pathStep
 	xkey, ykey int
+	isSlice    bool // False for reflect.Array
 }
 
 func (si SliceIndex) Type() reflect.Type             { return si.typ }
@@ -301,6 +305,72 @@ func (tf Transform) Func() reflect.Value { return tf.trans.fnc }
 // The == operator can be used to detect the exact option used.
 func (tf Transform) Option() Option { return tf.trans }
 
+// pointerPath represents a dual-stack of pointers encountered when
+// recursively traversing the x and y values. This data structure supports
+// detection of cycles and determining whether the cycles are equal.
+// In Go, cycles can occur via pointers, slices, and maps.
+//
+// The pointerPath uses a map to represent a stack; where descension into a
+// pointer pushes the address onto the stack, and ascension from a pointer
+// pops the address from the stack. Thus, when traversing into a pointer from
+// reflect.Ptr, reflect.Slice element, or reflect.Map, we can detect cycles
+// by checking whether the pointer has already been visited. The cycle detection
+// uses a seperate stack for the x and y values.
+//
+// If a cycle is detected we need to determine whether the two pointers
+// should be considered equal. The definition of equality chosen by Equal
+// requires two graphs to have the same structure. To determine this, both the
+// x and y values must have a cycle where the previous pointers were also
+// encountered together as a pair.
+//
+// Semantically, this is equivalent to augmenting Indirect, SliceIndex, and
+// MapIndex with pointer information for the x and y values.
+// Suppose px and py are two pointers to compare, we then search the
+// Path for whether px was ever encountered in the Path history of x, and
+// similarly so with py. If either side has a cycle, the comparison is only
+// equal if both px and py have a cycle resulting from the same PathStep.
+//
+// Using a map as a stack is more performant as we can perform cycle detection
+// in O(1) instead of O(N) where N is len(Path).
+type pointerPath struct {
+	// mx is keyed by x pointers, where the value is the associated y pointer.
+	mx map[value.Pointer]value.Pointer
+	// my is keyed by y pointers, where the value is the associated x pointer.
+	my map[value.Pointer]value.Pointer
+}
+
+func (p *pointerPath) Init() {
+	p.mx = make(map[value.Pointer]value.Pointer)
+	p.my = make(map[value.Pointer]value.Pointer)
+}
+
+// Push indicates intent to descend into pointers vx and vy where
+// visited reports whether either has been seen before. If visited before,
+// equal reports whether both pointers were encountered together.
+// Pop must be called if and only if the pointers were never visited.
+//
+// The pointers vx and vy must be a reflect.Ptr, reflect.Slice, or reflect.Map
+// and be non-nil.
+func (p pointerPath) Push(vx, vy reflect.Value) (equal, visited bool) {
+	px := value.PointerOf(vx)
+	py := value.PointerOf(vy)
+	_, ok1 := p.mx[px]
+	_, ok2 := p.my[py]
+	if ok1 || ok2 {
+		equal = p.mx[px] == py && p.my[py] == px // Pointers paired together
+		return equal, true
+	}
+	p.mx[px] = py
+	p.my[py] = px
+	return false, false
+}
+
+// Pop ascends from pointers vx and vy.
+func (p pointerPath) Pop(vx, vy reflect.Value) {
+	delete(p.mx, value.PointerOf(vx))
+	delete(p.my, value.PointerOf(vy))
+}
+
 // isExported reports whether the identifier is exported.
 func isExported(id string) bool {
 	r, _ := utf8.DecodeRuneInString(id)