prune: report how much data must be repacked to compressed the repo

prune now reports the remaining size of pack files containing
uncompressed blobs. The displayed value is suitable for use with `--max-repack-size`.

cmd/restic/cmd_prune.go

@@ -214,13 +214,14 @@ type pruneStats struct {
 		repackrm  uint
 	}
 	size struct {
-		used      uint64
-		duplicate uint64
-		unused    uint64
-		remove    uint64
-		repack    uint64
-		repackrm  uint64
-		unref     uint64
+		used         uint64
+		duplicate    uint64
+		unused       uint64
+		remove       uint64
+		repack       uint64
+		repackrm     uint64
+		unref        uint64
+		uncompressed uint64
 	}
 	packs struct {
 		used       uint
@@ -497,13 +498,16 @@ func decidePackAction(ctx context.Context, opts PruneOptions, gopts GlobalOption
 			stats.packs.partlyUsed++
 		}
 
+		if p.uncompressed {
+			stats.size.uncompressed += p.unusedSize + p.usedSize
+		}
 		mustCompress := false
 		if repoVersion >= 2 {
 			// repo v2: always repack tree blobs if uncompressed
 			// compress data blobs if requested
 			mustCompress = (p.tpe == restic.TreeBlob || opts.RepackUncompressed) && p.uncompressed
 		}
-		// use a flag that pack must be compressed
+		// use as flag that pack must be compressed
 		p.uncompressed = mustCompress
 
 		// decide what to do
@@ -602,6 +606,7 @@ func decidePackAction(ctx context.Context, opts PruneOptions, gopts GlobalOption
 		stats.size.repack += p.unusedSize + p.usedSize
 		stats.blobs.repackrm += p.unusedBlobs
 		stats.size.repackrm += p.unusedSize
+		stats.size.uncompressed -= p.unusedSize + p.usedSize
 	}
 
 	// calculate limit for number of unused bytes in the repo after repacking
@@ -633,6 +638,11 @@ func decidePackAction(ctx context.Context, opts PruneOptions, gopts GlobalOption
 	stats.packs.repack = uint(len(repackPacks))
 	stats.packs.remove = uint(len(removePacks))
 
+	if repo.Config().Version < 2 {
+		// compression not supported for repository format version 1
+		stats.size.uncompressed = 0
+	}
+
 	return prunePlan{removePacksFirst: removePacksFirst,
 		removePacks: removePacks,
 		repackPacks: repackPacks,
@@ -661,6 +671,9 @@ func printPruneStats(gopts GlobalOptions, stats pruneStats) error {
 	Verbosef("to delete:    %10d blobs / %s\n", stats.blobs.remove, ui.FormatBytes(stats.size.remove+stats.size.unref))
 	totalPruneSize := stats.size.remove + stats.size.repackrm + stats.size.unref
 	Verbosef("total prune:  %10d blobs / %s\n", stats.blobs.remove+stats.blobs.repackrm, ui.FormatBytes(totalPruneSize))
+	if stats.size.uncompressed > 0 {
+		Verbosef("not yet compressed:              %s\n", ui.FormatBytes(stats.size.uncompressed))
+	}
 	Verbosef("remaining:    %10d blobs / %s\n", totalBlobs-(stats.blobs.remove+stats.blobs.repackrm), ui.FormatBytes(totalSize-totalPruneSize))
 	unusedAfter := unusedSize - stats.size.remove - stats.size.repackrm
 	Verbosef("unused size after prune: %s (%s of remaining size)\n",