For those new to my project:

My GOG.com Files - http://bit.ly/1SDy4hH

Thankfully most of my unbundled games are old and/or small. (Blackwell series, Tomb Raider series,etc.) I just ran WinMerge on two folders at a time and was able to reduce things down a bit. Not too much had updated in them, so similarities were easy to find.

That doesn't work too well on larger files, though. Though, I think I recall seeing you have a lot more memory than I do (8GB), so maybe you'll have better luck doing something like that.

I also happened on a The Witcher installer that I had twice. One was .tar.gz, the other just .gz. Otherwise they were identical. That was a nice bit of freed space!

Thank you so much for the work you're doing!!


Edit: I hacked together a quick PHP script a few months back to convert the MaGog updates for my own owned games to RSS. I've pasted it on GitHub in case anyone finds it userful. It's not perfect, but it works somewhat.

https://gist.github.com/Shiryou/977f799942b68d6d1f054220b0370241

From MaGog's logs for 27 June:

---------------------------

A game has probably been added: Even the Ocean [Upcoming]

---------------------------

Windward has probably changed

[FILE UPDATES]

* File changed: Linux installer, English --- File name *FROM* gog_windward_2.32.0.35.sh *TO* gog_windward_2.33.0.36.sh --- File size *FROM* 73.9 MB *TO* 73.9 MB --- Date *FROM* Fri 24 Jun 2016 13:48:24 GMT *TO* Mon 27 Jun 2016 14:03:27 GMT --- Version *FROM* 2016-06-24 (gog-35) *TO* 2016-06-26.1 (gog-36)

* File changed: Mac OS X installer, English --- File name *FROM* windward_2.29.0.51.pkg *TO* windward_2.30.0.52.pkg --- File size *FROM* 71.6 MB *TO* 71.6 MB --- Date *FROM* Fri 24 Jun 2016 13:48:17 GMT *TO* Mon 27 Jun 2016 14:03:20 GMT --- Version *FROM* 2016-06-24 (gog-51) *TO* 2016-06-26.1 (gog-52)

* File changed: Windows installer, English --- File name *FROM* setup_windward_2.32.0.35.exe *TO* setup_windward_2.33.0.36.exe --- File size *FROM* 84.4 MB *TO* 84.4 MB --- Date *FROM* Fri 24 Jun 2016 13:48:12 GMT *TO* Mon 27 Jun 2016 14:03:13 GMT --- Version *FROM* 2016-06-24 (gog-35) *TO* 2016-06-26.1 (gog-36)

[CHANGELOG] available here.

---------------------------

Kona [In Dev] has probably changed

[FILE UPDATES]

* File added: Patch 20160616-01 (gog-5) [Linux] --- File size: 560.0 MB --- Version: 20160616-01 (gog-5)

* File changed: Linux installer, English --- File size *FROM* 2.2 GB *TO* 2.4 GB --- Version *FROM* 20160517-01 (gog-4) *TO* 20160616-01 (gog-5)

* File changed: Linux installer, French --- File size *FROM* 2.2 GB *TO* 2.4 GB --- Version *FROM* 20160517-01 (gog-4) *TO* 20160616-01 (gog-5)

* File changed: Mac OS X installer, English --- File size *FROM* 2.3 GB *TO* 2.4 GB --- Version *FROM* 20160517-01 (gog-7) *TO* 20160515-01 (gog-8)

* File changed: Mac OS X installer, French --- File size *FROM* 2.3 GB *TO* 2.4 GB --- Version *FROM* 20160517-01 (gog-7) *TO* 20160515-01 (gog-8)

* File changed: Windows installer, English (part 1 of 2) --- Size has not changed --- Version *FROM* 20160517-01 (gog-14) *TO* 20160616-01 (gog-15)

* File changed: Windows installer, English (part 2 of 2) --- File size *FROM* 2.1 GB *TO* 2.2 GB --- Version *FROM* 20160517-01 (gog-14) *TO* 20160616-01 (gog-15)

* File changed: Windows installer, French (part 1 of 2) --- Size has not changed --- Version *FROM* 20160517-01 (gog-14) *TO* 20160616-01 (gog-15)

* File changed: Windows installer, French (part 2 of 2) --- File size *FROM* 2.1 GB *TO* 2.2 GB --- Version *FROM* 20160517-01 (gog-14) *TO* 20160616-01 (gog-15)

[CHANGELOG] available here.

---------------------------

Wolcen: Lords of Mayhem [In Dev] has probably changed

[FILE UPDATES]

* File changed: Windows installer, English (part 1 of 3) --- Size has not changed --- Version *FROM* 0.2.3 (gog-9) *TO* 0.2.4 (gog-10)

* File changed: Windows installer, English (part 2 of 3) --- Size has not changed --- Version *FROM* 0.2.3 (gog-9) *TO* 0.2.4 (gog-10)

* File changed: Windows installer, English (part 3 of 3) --- Size has not changed --- Version *FROM* 0.2.3 (gog-9) *TO* 0.2.4 (gog-10)

[CHANGELOG] available here.

---------------------------

8-bit Armies has probably changed

[FILE UPDATES]

* File changed: Windows installer, English --- Size has not changed --- Version *FROM* 0.73.612289b (gog-20) *TO* 0.73.612831 (gog-21)

[CHANGELOG] available here.

---------------------------

I've got one directory set as the download directory where Galaxy downloads to (and formerly GOG Downloader which I still have but rarely ever use anymore as well), and a second directory named "GOG Galaxy Archives" which is where I manually move the downloaded directories for new games to, and manually peruse newly downloaded files for games that pre-exist in the archives then figure out what to do with them on a game by game file by file basis. Normally it takes only a few seconds per game, but sometimes filenames change or get added or removed and additional sleuthing needs to be done. Some of those are simple enough to figure out or to ask around the forums to get info and sort it out, but others I leave sitting in the Download folder for a rainy day when I'm bored. :)

Then I have my old downloads also from the pre-unbundle days, some of which I want to keep archived in bundled form, and others which I'm ok to get rid of once I determine for sure that the newer unbundled versions are equal or better replacements using my own personal metrics. So I have maybe a dozen or so games in "limbo" state currently that I need to sort out eventually. They don't take up much space though as I took care of the disk gobblers already. :)

Yeah, 32GB of RAM is quiet cozy. :)

While I'm a pretty severe Linux geek and have had my fun over the years tinkering with gaming in Linux on and off, for years now I've kept my gaming strictly in Windows, as such even though I look forward to doing so sometime in the non-distant future - I have not yet embraced current generation Linux gaming on GOG, Steam or elsewhere. If I had a spare PC that was powerful enough that I could dedicate to it I probably would, but that's not in my cards at the moment for worse or worse. :) Having said that, I do not download the Linux binaries, nor any Linux specific bonus extras yet, as I'm already bursting the seams of my HDDs just keeping up with the Windows backups. If I did download Linux backups though and they were in tar.gz or other legacy archive formats, I have to admit that I would be extremely highly tempted to rearchive them as .tar.xz archives with custom options passed to xz to let it really rape my CPU and RAM to its advantage to shrink the files maximally.

If GOG isn't doing that already I'd have to be surprised because xz is amazingly efficient and reasonably low resource usage on decompression, and always has much smaller files than .gz, .zip or any other legacy archive compression formats. xz is only CPU/RAM burdensome on the compression phase, which can be very resource exhausting, but that only happens once. Hopefully they switch to using xz/LZMA2 in the future if they aren't already (on all platforms).

They probably corrected the metadata error incorrectly reporting that the 1.22 version files were version 1.21 is my best guess, although I have no way of verifying that. I did redownload the files though and they're newer than what I had.

My current Windows install is getting a bit old and slow. I'm considering getting a new computer and then using this one as a dedicated Linux box. I never did get enough time to play with Linux. Maybe I'll just leave it as Linux for a while before replacing. Or I could take the leap and install Windows 10 and see how that looks. Decisions, decisions.

IEEEEE!!! Yeah, go with Linux for sure on that box. :)

8-Bit Armies updated:

Patch 0.73.612831 (27 June 2016)

NEW FEATURES:

* Quickmatch (Player Requested): Multiplayer now provides an option to randomly match against another player of an equal skill setting in 1v1 using our internal Elo rating system. Maps are randomly selected from an approved list selected and updated by the design team. All matches use standard victory condition, with 10k resources, and crates turned off. Players need only select Quickmatch and then choose their faction.

GENERAL IMPROVEMENTS:

* Fix for issue in which infantry were still playing their run sounds even while being transported
* Removed delay before playing the movie when surrendering or while in the tutorial
* Fixed issue related to the AI firing a superweapon after the relevant structure had already been destroyed
* Font support for German language characters Ä, Ö, Ü, and ß for upcoming translation release

Subterrain

Patch 1122 (28th June 2016)

Fixed : Possible solution for time flow simulation getting messed up by Unity floating bug. Implemented custom way of checking and increasing precision internally. This should hopefully fix the cases where after playing for long time, weapon cool down and production timing getting messed up.

Updated : Increased storage weight limit to prevent inventory bug to happen when interacting with storage.

Ooops, thanks for that! Yesterday I run the script with a missing parameter and as a consequence I didn't get the changelogs. I'll just edit that post to add them... :S

EDIT: Nope, I can't. The new changelogs are too long and they won't fit in a single message. I'll just put them in my next posts.

Missing changelogs from yesterday:

---------------------------

Windward

[CHANGELOG UPDATED]

2016-06-26.1 (27th June 2016)

- Reduced dragon’s HP by 40% and damage by 33%.
- Dragons will no longer use hasty repairs while in combat, allowing for them to break sight of players for 10 seconds before they begin to heal.
- Removed dragon’s chance of getting a Reckless Volley. Reckless Volley has a built-in crit chance, and critting dragons are bad, mmkay?
- Dropped Nether dragon’s essence’s stats should now function properly.
- Dropping the dragon’s health down to 75%, 50% and 25% will now reward players with legendary loot.
- Loot dropped by units defeated above land will now appear above the surface.
- Loot crates will now last 5-10 minutes (up from 3), depending on the loot’s quality.
- Loot spawned when defeating something outside the region’s bounds will now appear closer to the center.
- Added a Telescope – a better version of the Spyglass tool.
- If a player doesn’t damage anyone when the dragon’s curse ends, they will now be granted a new buff for 30 seconds increasing their hull, damage and diplomacy and preventing them from getting cursed again for the duration.
- AI will no longer try to ram anything if their sails are below 70%.
- Dragons will now ignore cursed players and will focus on others instead.
- Dragons will now keep their distance better and will not try to circle around players. They will get closer to use the breath, however.
- Dragons’ decision which enemy to attack will now become more erratic as they get hurt.
- Dragons will no longer curse the only player in sight. They will wait for others to show up.
- Guard towers will no longer crit.
- Siege towers will now use bigger ammunition.
- It’s now possible to leave the /observer mode in an instance without getting removed from the instance.
- 26.1: Fix for some ships not applying cannonball damage properly.

2016-06-25

- King-reflected IWIN will now only kill the player that used the skill and that player’s respawn timer will be greatly increased for the next respawn.
- Made it possible to properly work with arbitrary asset bundles uploaded to the server. Example: load and play custom sounds. (playing them is a dev build ability for now)
- Players killed by king tier or higher mobs will now have their respawn timers increased to 25 seconds for the next respawn (same as during the dragon fight).
- Combat and heroic regions now have a forced minimum size of 256.
- Heroic tier NPCs will now have resistances up to 30% and vulnerabilities up to 20% (up from 10% and 10%).
- Added a new Raid type instance. A little more difficult than a heroic but with better loot and has a dragon boss at the end. Very likely to be altered in a future update, as right now it’s pretty much just a heroic with a different boss, and starts with half the region controlled by the ”cultists”.
- Dragon defeated at the end of the Raid instance will now drop Nether resistance loot as well as essences. Admin intervention is no longer needed.
- Dragon loot now requires at least 6 players to be present in order to drop.
- Completion quest for heroics that always awards a legendary item now requires at least 2 players to be present. Raid quest requires 6. The loot inside can still be gathered solo for a well equipped player. Only the completion rewards have this limitation.
- Ship explosions should no longer affect loot crates.
- Added a new /open command that the person that started the instance can use. This will make it possible for players to right-click the name of any of the players in that instance and choose the “Join” option to join it automatically.
- Combat instances will no longer give the completion reward if there are fewer than 4 towns in the region.
- 25.1: Fixed a harmless error that was showing up during the dragon fight.

---------------------------

Kona [In Dev]

[CHANGELOG UPDATED]

Patch 20160616-01 (27 June 2016)
Interactors
Most of the feedback we receive is about our user interface. We’ve decided to change all interactors to make things clearer.
From now on, every interactor you will see will be a little square (see image). When you approach, the square will turn a little and you will be able to interact with the object. If you don’t know what action it might trigger, you will see a brief description or a small image of what the interactor does after a few seconds.
No More Combine Menu
We decided to remove the combine menu. Instead, when you have all required items, you will need to hold the interaction key (usually the E key or the A button on a controller) until the bar is full. Since our game doesn’t really focus on crafting, why not find a simpler way to do so!
Known issues
Here are some of the known issues that we are already working on fixing:

- The mouse scroll for texts works now. However, some the W and S buttons don’t work in all of them;
- When you have the lantern equiped (and sometimes with the flashlight) and you smoke a cigarette, the lantern is still in your hands until the end of the animation.

---------------------------

Wolcen: Lords of Mayhem [In Dev]

[CHANGELOG UPDATED]

Patch 0.2.4 (27th June 2016)
Note: Due to a refactor of many gameplay elements, old saves are not compatible with this version. Please excuse us for the inconvenience. Please remember that the game is still in Early Access, and this kind of character reset may happen quite often.
GENERAL:

- Fixed: Your progression is now correctly saved when going back to main menu.
- Fixed: Books no longer appear on the Amarth's waypoint when sold to the merchant.
- Fixed: Templars and enemies now all have their weapons in hand
- Fixed: The hero model don't appear in the character selection pannel if you have no character created

ENVIRONMENT:

- New: Villagers in Amarth
- New: Particle FX on waypoints
- Improved: reduce fog density during night time
- Improved: SVOTU diffuse bias is now 0.05
- Improved: Waypoints now have smaller selection range
- Modified: Waypoints outline is now blue instead of yellow.
- Fixed: rain in dungeons
- Fixed: some navmesh bad connections in randomly generated dungeons
- Fixed: Luthor's stash particle now disappears when the object is picked up.
- Fixed: some layer switch override problems
- Fixed: Multiple spellbooks issue.
- Fixed: Rare bug where time of day would not set when entering a randomly generated dungeon

IA:

- New: Butchers can now hit surrounding mobs.
- Fixed: Mobs should now properly target the player when using melee charge.

UI:

- New: Antialiasing modes in advanced graphic settings (SMAA 1X, SMAA 1TX, SMAA 2TX)
- New: Vignetting in advanced graphic settings
- Modified: Localization update by the community: Korean, Chinese, German, Hungarian. Thanks guys!
- Improved: Death screen (now animated)
- Fixed: Player position is now correctly displayed on the world map.
- Fixed: Minimap no longer appear in the player's health globe
- Fixed: Can no longer open the world map in the main menu or in the pause menu
- Fixed: Main menu does not show the game in background anymore
- Fixed: Remaining stats points are now correctly displayed after death
- Fixed: Incorrect stats requierements displayed on item details panel
- Fixed: Prevent default skills (combos, charged attacks) to be overriden by other skills.

GAMEPLAY:

- New weapon: Woodcutter axe
- New: Charged attacks for each weapon class, except one handed.
- New: Shield block
- Modified: Utility and power skill upgrades nerfed
- Fixed: Lightning damage are now correctly affected by water (+100%) and rain (+10%).
- Fixed: Damage reduction is now correctly calculated for lightning spread.
- Fixed: Destroyable objects no longer give rage when hit.
- Fixed: Proper orientation of player when casting skills.
- Fixed: Teleportation bug where player got stuck in the environment.
- Fixed: Expulse blows (Skullcrusher) and charge from orc chargers shouldn't hit the player anymore if he is too far away.
- Fixed: The Zombie charge attack now hits properly.
- Fixed: You can no longer teleport from anywhere on the map. You now have to be near a waypoint.
- Fixed: You can now chain skill casting properly while holding keys.
- Fixed: Holding both mouse buttons no longer stops the player if you can't cast the right button skill.
- Fixed: Luthor's stash does not appear after the quest's end anymore
- Fixed: Camera now correctly follows the player when teleporting
- Fixed: A rare crash when using the Deep Strike spell.

CHARACTERS:

- New : Multi peasants.
- Fixed: The shield no longer disappears when another weapon is equipped.
- Fixed: Spiders now bleed correctly (and have new dark green blood particles and decals).
- Fixed: Fixed a rare bug where the player would fall through the map when entering a dungeon

ANIMATION:

- New: peasant animations
- New: skeletons_giant attack
- Various animations for spider, ghoul, ogre and player added and modified

KNOWN ISSUES

- • White flashes can appear the first time the game in launched, at the exit of the cave. This is due to compiling shaders.
- • Using charged attacks and default attack is not very fluid at the moment. It will be updated soon
- • Loot icons stuttering happens sometime and will be fixed in a future update – The whole system will change

---------------------------

*surprise*
the Linux installers are compressed with zip. The windows installer still use rar I believe.

while I had intention in the past to repackage the Linux installers before storing them, I mostly abandoned that. Don't think it is worth the time. If GOG where to make that step that would be marvelous. I would be happy about the shortened download time. But a few GB saved on storage space? With todays HDD sizes? meh, not worth the effort

Changelogs for </span></i>, <i><span class="bold">[url=https://www.gog.com/forum/windward/changelog/post7]Windward, and Thea: The Awakening added to each game forum.

From MaGog's logs for 28 June:

---------------------------

Thea: The Awakening has probably changed


[FILE UPDATES]

* File added: Patch 1.20.1827 (gog-8) --- File name: patch_thea_the_awakening_2.6.0.8.exe --- File size: 6.8 MB --- Date: Tue 28 Jun 2016 11:50:34 GMT --- Version: 1.20.1817 (gog-7) -> 1.20.1827 (gog-8)

* File changed: Patch 1.16.1712 (gog-6) --- File name has not changed --- Size has not changed --- Date has not changed --- Version *FROM* 1.16.1712 (gog-5) -> Patch 1.16.1712 (gog-6) *TO* 1.16.1712 (gog-5) -> 1.16.1712 (gog-6)

* File changed: Windows installer, English+French+German+Polish+Russian --- File name *FROM* setup_thea_the_awakening_2.5.0.7.exe *TO* setup_thea_the_awakening_2.6.0.8.exe --- Size has not changed --- Date *FROM* Thu 23 Jun 2016 15:14:16 GMT *TO* Tue 28 Jun 2016 11:52:31 GMT --- Version *FROM* 1.20.1817 (gog-7) *TO* 1.20.1827 (gog-8)

* File changed: story bundle (additional in-game events) --- File name *FROM* thea_story_bundle.zip *TO* thea_story_bundle_1_20_1827.zip --- File size *FROM* 62.9 KB *TO* 63.0 KB --- Date *FROM* Thu 23 Jun 2016 16:48:38 GMT *TO* Tue 28 Jun 2016 11:53:37 GMT --- Version has not changed


[CHANGELOG UPDATED]

Patch 1.20.1827 (28 June 2016)
All game versions:

- 2H Hammers cost only 1 research point,
- 2H Hammers do a bit more damage,
- 2H Axes do a bit more damage,
- All resources in Straw tree cost only 1 point to unlock,
- Within the village's gathering area, movement cost is lowered to 1 for player expeditions. This area grows if there is a Blessed Path building in the village,
- Changes to calculations for death chance in Bloodbath mode,
- Fixed a dwarf model not being shown on the map,
- Fixed text on an inventory item that would overflow its textfield if it was too long.
- Events fixes.

Story Bundle (bonus download):

- Events fixes.

MultiPrayer:

- Ability to select server location for connection by name [layout needs to be improved though]
- More messages informing why connection failed for connection by name,
- Improved attraction rates for children to slightly counter the more difficult starting conditions (closer to higher level areas, with smaller population and with no children)
- Improved attraction rates in SNAIL MODE,
- End turn can be "undone" as long as the other player has not finished their turn [needs new artwork]

---------------------------

Subterrain has probably changed


[FILE UPDATES]

* File changed: Windows installer, English --- File size *FROM* 423.0 MB *TO* 444.0 MB --- Version *FROM* 1118 (gog-11) *TO* 1122 (gog-12)


[CHANGELOG UPDATED]

Patch 1122 (28th June 2016)

- Fixed : Possible solution for time flow simulation getting messed up by Unity floating bug. Implemented custom way of checking and increasing precision internally. This should hopefully fix the cases where after playing for long time, weapon cool down and production timing getting messed up.
- Updated : Increased storage weight limit to prevent inventory bug to happen when interacting with storage.

---------------------------

Most people would probably feel similar. It'd be easy enough to script though or toss into a cron job in Linux. Possibly might require script modifications or similar to work, I'm not familiar with how GOG has the Linux games packaged but I'd probably hack around on the stuff and see what kind of savings could be had. From personal experience with archiver testing in Linux over the years though and in particular with packaging software, I can say for certain that using xz/LZMA compression gives a generally dramatic savings in file size. You could shrink the files anywhere up to 30% or more depending on the contents, with 20-25% very common in my experience. With 400GB of games, that could translate to 100GB of savings, which isn't much with 6TB drives on the market etc. but many people would appreciate the savings, plus the decompression is faster, so there would be a performance improvement potentially as well.

Would need some solid testing to see real results though. I'll do that some day in the future if someone hasn't beaten me to it by then. :)

"depending on the contents" being the important keyword here ;)
if the game assets are already well compressed because the developer aimed to reduce disc IO/loading time, then any additional compression probably won't give dramatic savings anyway. And music/video files usually will give you hardly any compression at all.
Not sure that decompression time will improve. In my experience zip still beats xz in terms of speed.

There have been people here in the forum who have done and published some more detailed benchmarks.
Not quite sure where to find those posts though ;)
might have been in the stickied linux thread iirc