Allow disabling bzip2 compression for index files

Using bzip2 generates smaller index files (roughly 20% smaller Packages
files) but it comes with a big performance penalty.  When publishing a
debian mirror snapshot (amd64, arm64, armhf, source) without contents
skipping bzip speeds things up around 1.8 times.

```
$ hyperfine -w 1 -L skip-bz2 true,false  -m 3 -p "aptly -config aptly.conf publish drop bullseye || true" "aptly -config aptly.conf  publish snapshot  --skip-bz2={skip-bz2} --skip-contents --skip-signing bullseye"
Benchmark 1: aptly -config aptly.conf  publish snapshot  --skip-bz2=true --skip-contents --skip-signing bullseye
  Time (mean ± σ):     35.567 s ±  0.307 s    [User: 39.366 s, System: 10.075 s]
  Range (min … max):   35.311 s … 35.907 s    3 runs

Benchmark 2: aptly -config aptly.conf  publish snapshot  --skip-bz2=false --skip-contents --skip-signing bullseye
  Time (mean ± σ):     64.740 s ±  0.135 s    [User: 68.565 s, System: 10.129 s]
  Range (min … max):   64.596 s … 64.862 s    3 runs

Summary
  'aptly -config aptly.conf  publish snapshot  --skip-bz2=true --skip-contents --skip-signing bullseye' ran
    1.82 ± 0.02 times faster than 'aptly -config aptly.conf  publish snapshot  --skip-bz2=false --skip-contents --skip-signing bullseye'
```

Allow skipping bz2 creation for setups where faster publishing is more
important then Package file size.

Signed-off-by: Sjoerd Simons <sjoerd@collabora.com>

cmd/publish_repo.go

@@ -42,6 +42,7 @@ Example:
 	cmd.Flag.Bool("batch", false, "run GPG with detached tty")
 	cmd.Flag.Bool("skip-signing", false, "don't sign Release files with GPG")
 	cmd.Flag.Bool("skip-contents", false, "don't generate Contents indexes")
+	cmd.Flag.Bool("skip-bz2", false, "don't generate bzipped indexes")
 	cmd.Flag.String("origin", "", "origin name to publish")
 	cmd.Flag.String("notautomatic", "", "set value for NotAutomatic field")
 	cmd.Flag.String("butautomaticupgrades", "", "set  value for ButAutomaticUpgrades field")

cmd/publish_snapshot.go

@@ -139,6 +139,11 @@ func aptlyPublishSnapshotOrRepo(cmd *commander.Command, args []string) error {
 		published.SkipContents = context.Flags().Lookup("skip-contents").Value.Get().(bool)
 	}
 
+	published.SkipBz2 = context.Config().SkipBz2Publishing
+	if context.Flags().IsSet("skip-bz2") {
+		published.SkipBz2 = context.Flags().Lookup("skip-bz2").Value.Get().(bool)
+	}
+
 	if context.Flags().IsSet("acquire-by-hash") {
 		published.AcquireByHash = context.Flags().Lookup("acquire-by-hash").Value.Get().(bool)
 	}
@@ -228,6 +233,7 @@ Example:
 	cmd.Flag.Bool("batch", false, "run GPG with detached tty")
 	cmd.Flag.Bool("skip-signing", false, "don't sign Release files with GPG")
 	cmd.Flag.Bool("skip-contents", false, "don't generate Contents indexes")
+	cmd.Flag.Bool("skip-bz2", false, "don't generate bzipped indexes")
 	cmd.Flag.String("origin", "", "overwrite origin name to publish")
 	cmd.Flag.String("notautomatic", "", "overwrite value for NotAutomatic field")
 	cmd.Flag.String("butautomaticupgrades", "", "overwrite value for ButAutomaticUpgrades field")

cmd/publish_switch.go

@@ -96,6 +96,10 @@ func aptlyPublishSwitch(cmd *commander.Command, args []string) error {
 		published.SkipContents = context.Flags().Lookup("skip-contents").Value.Get().(bool)
 	}
 
+	if context.Flags().IsSet("skip-bz2") {
+		published.SkipBz2 = context.Flags().Lookup("skip-bz2").Value.Get().(bool)
+	}
+
 	err = published.Publish(context.PackagePool(), context, collectionFactory, signer, context.Progress(), forceOverwrite)
 	if err != nil {
 		return fmt.Errorf("unable to publish: %s", err)
@@ -153,6 +157,7 @@ This command would switch published repository (with one component) named ppa/wh
 	cmd.Flag.Bool("batch", false, "run GPG with detached tty")
 	cmd.Flag.Bool("skip-signing", false, "don't sign Release files with GPG")
 	cmd.Flag.Bool("skip-contents", false, "don't generate Contents indexes")
+	cmd.Flag.Bool("skip-bz2", false, "don't generate bzipped indexes")
 	cmd.Flag.String("component", "", "component names to update (for multi-component publishing, separate components with commas)")
 	cmd.Flag.Bool("force-overwrite", false, "overwrite files in package pool in case of mismatch")
 	cmd.Flag.Bool("skip-cleanup", false, "don't remove unreferenced files in prefix/component")

cmd/publish_update.go

@@ -60,6 +60,10 @@ func aptlyPublishUpdate(cmd *commander.Command, args []string) error {
 		published.SkipContents = context.Flags().Lookup("skip-contents").Value.Get().(bool)
 	}
 
+	if context.Flags().IsSet("skip-bz2") {
+		published.SkipBz2 = context.Flags().Lookup("skip-bz2").Value.Get().(bool)
+	}
+
 	err = published.Publish(context.PackagePool(), context, collectionFactory, signer, context.Progress(), forceOverwrite)
 	if err != nil {
 		return fmt.Errorf("unable to publish: %s", err)
@@ -112,6 +116,7 @@ Example:
 	cmd.Flag.Bool("batch", false, "run GPG with detached tty")
 	cmd.Flag.Bool("skip-signing", false, "don't sign Release files with GPG")
 	cmd.Flag.Bool("skip-contents", false, "don't generate Contents indexes")
+	cmd.Flag.Bool("skip-bz2", false, "don't generate bzipped indexes")
 	cmd.Flag.Bool("force-overwrite", false, "overwrite files in package pool in case of mismatch")
 	cmd.Flag.Bool("skip-cleanup", false, "don't remove unreferenced files in prefix/component")