aptly snapshot diff command and documentation.

README.rst

@@ -412,6 +412,33 @@ Example::
     Snapshot snap-deb-main-w-xorg successfully created.
     You can run 'aptly publish snapshot snap-deb-main-w-xorg' to publish snapshot as Debian repository.
 
+``aptly snapshot diff``
+^^^^^^^^^^^^^^^^^^^^^^^
+
+Displays difference in packages between two snapshots. Snapshot is a list of packages, so difference between
+snapshots is a difference between package lists. Package could be either completely missing in one snapshot,
+or package is present in both snapshots with different versions.
+
+Usage::
+
+ aptly snapshot diff <name-a> <name-b>
+
+Options:
+
+* ``-only-matching=false``: display diff only for matching packages (don't display missing packages)
+
+Example::
+
+  $ aptly snapshot diff snap-deb2-main snap-deb-main-w-xorg
+    Arch   | Package                                  | Version in A                             | Version in B
+  ! amd64  | libxfont1                                | 1:1.4.1-3                                | 1:1.4.4-1~bpo60+1
+  ! i386   | libxfont1                                | 1:1.4.1-3                                | 1:1.4.4-1~bpo60+1
+  ! all    | xserver-common                           | 2:1.7.7-16                               | 2:1.10.4-1~bpo60+2
+  ! amd64  | xserver-xorg                             | 1:7.5+8+squeeze1                         | 1:7.6+8~bpo60+1
+  ! i386   | xserver-xorg                             | 1:7.5+8+squeeze1                         | 1:7.6+8~bpo60+1
+  ! amd64  | xserver-xorg-core                        | 2:1.7.7-16                               | 2:1.10.4-1~bpo60+2
+  ! i386   | xserver-xorg-core                        | 2:1.7.7-16                               | 2:1.10.4-1~bpo60+2
+
 Command ``publish``
 ~~~~~~~~~~~~~~~~~~~
 

cmd_snapshot.go

@@ -343,6 +343,90 @@ func aptlySnapshotPull(cmd *commander.Command, args []string) error {
 	return err
 }
 
+func aptlySnapshotDiff(cmd *commander.Command, args []string) error {
+	var err error
+	if len(args) != 2 {
+		cmd.Usage()
+		return err
+	}
+
+	onlyMatching := cmd.Flag.Lookup("only-matching").Value.Get().(bool)
+
+	snapshotCollection := debian.NewSnapshotCollection(context.database)
+	packageCollection := debian.NewPackageCollection(context.database)
+
+	// Load <name-a> snapshot
+	snapshotA, err := snapshotCollection.ByName(args[0])
+	if err != nil {
+		return fmt.Errorf("unable to load snapshot A: %s", err)
+	}
+
+	err = snapshotCollection.LoadComplete(snapshotA)
+	if err != nil {
+		return fmt.Errorf("unable to load snapshot A: %s", err)
+	}
+
+	// Load <name-b> snapshot
+	snapshotB, err := snapshotCollection.ByName(args[1])
+	if err != nil {
+		return fmt.Errorf("unable to load snapshot B: %s", err)
+	}
+
+	err = snapshotCollection.LoadComplete(snapshotB)
+	if err != nil {
+		return fmt.Errorf("unable to load snapshot B: %s", err)
+	}
+
+	// Calculate diff
+	diff, err := snapshotA.RefList().Diff(snapshotB.RefList(), packageCollection)
+	if err != nil {
+		return fmt.Errorf("unable to calculate diff: %s", err)
+	}
+
+	if len(diff) == 0 {
+		fmt.Printf("Snapshots are identical.\n")
+	} else {
+		fmt.Printf("  Arch   | Package                                  | Version in A                             | Version in B\n")
+		for _, pdiff := range diff {
+			if onlyMatching && (pdiff.Left == nil || pdiff.Right == nil) {
+				continue
+			}
+
+			var verA, verB, pkg, arch, code string
+
+			if pdiff.Left == nil {
+				verA = "-"
+				verB = pdiff.Right.Version
+				pkg = pdiff.Right.Name
+				arch = pdiff.Right.Architecture
+			} else {
+				pkg = pdiff.Left.Name
+				arch = pdiff.Left.Architecture
+				verA = pdiff.Left.Version
+				if pdiff.Right == nil {
+					verB = "-"
+				} else {
+					verB = pdiff.Right.Version
+				}
+			}
+
+			if pdiff.Left == nil {
+				code = "@g+@|"
+			} else {
+				if pdiff.Right == nil {
+					code = "@r-@|"
+				} else {
+					code = "@y!@|"
+				}
+			}
+
+			color.Printf(code+" %-6s | %-40s | %-40s | %-40s\n", arch, pkg, verA, verB)
+		}
+	}
+
+	return err
+}
+
 func makeCmdSnapshotCreate() *commander.Command {
 	cmd := &commander.Command{
 		Run:       aptlySnapshotCreate,
@@ -424,6 +508,22 @@ process.
 	return cmd
 }
 
+func makeCmdSnapshotDiff() *commander.Command {
+	cmd := &commander.Command{
+		Run:       aptlySnapshotDiff,
+		UsageLine: "diff <name-a> <name-b>",
+		Short:     "calculates difference in packages between two snapshots",
+		Long: `
+Displays list of missing and new packages, difference in package versions between two snapshots.
+`,
+		Flag: *flag.NewFlagSet("aptly-snapshot-diff", flag.ExitOnError),
+	}
+
+	cmd.Flag.Bool("only-matching", false, "display diff only for matching packages (don't display missing packages)")
+
+	return cmd
+}
+
 func makeCmdSnapshot() *commander.Command {
 	return &commander.Command{
 		UsageLine: "snapshot",
@@ -434,6 +534,7 @@ func makeCmdSnapshot() *commander.Command {
 			makeCmdSnapshotShow(),
 			makeCmdSnapshotVerify(),
 			makeCmdSnapshotPull(),
+			makeCmdSnapshotDiff(),
 			//makeCmdSnapshotDestroy(),
 		},
 		Flag: *flag.NewFlagSet("aptly-snapshot", flag.ExitOnError),