Ciro Santilli @cirosantilli 37

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Endurance sport Updated 2025-07-16

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List of sports Updated 2025-07-16

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Lists of mathematical problems Updated 2025-07-16

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Good place to hunt for the beauty of mathematics.

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Mailing list Updated 2025-07-16

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It boggles Ciro Santilli's mind that people use mailing list to collaborate on projects!

The only explanation is that the dinosaurs who created the projects are unable to adapt to new superior technologies.

Yes, Ciro is talking to you, big fundamental projects from last century: Linux kernel, GNU Compiler Collection (gcc.gnu.org/lists.html), Binutils (sourceware.org/binutils/), etc.

Some of you are already using Bugzilla for the bugs, so kudos. But if you've seen their benefit, why you still use the mailing list for patches?

Advantages of mailing lists:

threaded replies, which almost no issue tracker has. GitHub feature request: github.com/isaacs/github/issues/837

Disadvantages: everything else:

cannot subscribed to a single thread. Which forces you to create an email filter for each one of them you subscribe to.
no metadata, notably the notion of closing / merging, but also upvotes
You have to read thirty messages before you can know if the bug was solved or not.
it is insanely hard to reply to messages from before you were subscribed: webapps.stackexchange.com/questions/23197/reply-to-mailman-archived-message/115088#115088
This forces everyone to subscribe to all lists, and then set up email filters to not be flooded with emails.
hard to apply patches locally to test them out: stackoverflow.com/questions/5062389/how-to-use-git-am-to-apply-patches-from-email-messages/49082916#49082916
Unless they use Patchwork, which adds one more website on top of the mess.
And then Gmail corrupts your patches, and you are forced to use git send-email, which does not work on some network configurations: stackoverflow.com/questions/28038662/how-to-solve-unable-to-initialize-smtp-properly-when-using-using-git-send-ema or setup ThunderBird.
often have to subscribe to post at all, thus cluttering your inbox further
you can edit posts to make them clearer.
Yes, people could vandalize their answers when they get mad, and threads might stop making sense after edits. But this can be solved with an undeletable post history like Stack Overflow has (but not any other tracker does).
Or archive.org :-)
In any case, what do you think will happen more often and have greater impact:
- people vandalize their posts
- people fix their silly typos and improve content
searchable by author, keyword, etc. without Google. Yes, mailing list trackers could have decent implementations to overcome that. But no, GNU Mailman which everyone uses does not have it. Google barely indexes it.
And I don't think Google properly indexes many of the mailing list archives for some reason: I never get hits for my own posts a week later, while I often do on GitHub issues.
people have to learn about top posting vs inline posting, and this requires infinite education of new users
Line comments in code reviews like GitHub and GitLab.
On mailing lists: either put a comment in the middle of a huge patch and let other people find it, or (more likely) copy paste the part of the patch that you are talking about.
most mail web UIs suck.
OK, this is not an unsolvable or intrinsic problem, but still a problem.
E.g.: ezmlm it is not possible to see the entire content in a single page: gcc.gnu.org/ml/gcc/2015-07/threads.html.
Unless you like reading threads backwards and with 4 levels of > quotations.
The alternative: do like LLVM and send attachments. Yes, I we all love opening up attachments on our browsers.
The real solution: everyone can create branches and pull requests. Also has the benefit of running CI on the pull requests.

Not sure:

you can have infinitely many trackers to replicate data in case apocalypse happens in some part of the world.
Although I'm not sure this is an advantage, as you don't know anymore which one is the canonical trackers an advantage, as you don't know anymore which one is the canonical tracker.
And all web interfaces already have an API to export messages, and someone has already scripted it to import from any web UI to any web UI for you.
And GitHub offers infinite precise history transparently on its API.

Smart people who agree with Ciro:

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Online marketplace Updated 2025-07-16

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Review site Updated 2025-07-16

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Git tips / diff3 Updated 2025-07-16

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diff3 conflict is basically what you always want to see, either by setting it as the default as per stackoverflow.com/questions/27417656/should-diff3-be-default-conflictstyle-on-git:

git config --global merge.conflictstyle diff3

or as a one off:

git checkout --conflict=diff3

With this, conflicts now show up as:

++<<<<<<< HEAD
 +5
++||||||| parent of 7b0f59d (6)
++3
++=======
+ 6
++>>>>>>> 7b0f59d (6)

7b0f59d is the SHA-2 of commit 6.

instead of the inferior default:

++<<<<<<< ours
 +5
++=======
+ 6
++>>>>>>> theirs

We can also observe the current tree state during resolution:

* b4ec057 (HEAD, master) 5
* 0b37c1b 4
| * fbfbfe8 (my-feature) 7
| * 7b0f59d 6
|/
* 661cfab 3
* 6d748a9 2
* c5f8a2c 1

so we understand that we are now at 5 and that we are trying to apply our commit 6

So it is much clearer what is happening:

master changed the code from 3 to 5
our feature changed the code from 3 to 6

and so now we have to decide what the new code is that will put both of these together.

Let's say we decide it is 5 + 6 = 11 and continue rebasing:

git add .
git rebase --continue

We now reach:

++<<<<<<< HEAD
 +11
++||||||| parent of fbfbfe8 (7)
++6
++=======
+ 7
++>>>>>>> fbfbfe8 (7)

and the tree looks like:

* ca7f7ff (HEAD) 6
* b4ec057 (master) 5
* 0b37c1b 4
| * fbfbfe8 (my-feature) 7
| * 7b0f59d 6
|/
* 661cfab 3
* 6d748a9 2
* c5f8a2c 1

So we understand that:

after the previous step we added commit 6 on top of 5
now we are adding 7 on top of the new 6 (which we decided would contain 11)

and after resolving that one we now reach:

* e1aaf20 (HEAD -> my-feature) 7
* ca7f7ff 6
* b4ec057 (master) 5
* 0b37c1b 4
* 661cfab 3
* 6d748a9 2
* c5f8a2c 1

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Git tips / It's not a tree, it's actually a DAG Updated 2025-07-16

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Every tree is a directed acyclic graph.

But not every directed acyclic graph is a tree.

Example of a tree (and therefore also a DAG):

5
|
4 7
| |
3 6
|/
2
|
1

Convention in this presentation: arrows implicitly point up, just like in a git log, i.e.:

1 is parent of 2
2 is parent of 3 and 6
3 is parent of 4

and so on.

Example of a DAG that is not a tree:

7
|\
4 6
| |
3 5
|/
2
|
1

This is not a tree because there are two ways to reach 7:

2, 3, 4, 7
2, 5, 6, 7

But we often say "tree" intead of "DAG" in the context of Git because DAG sounds ugly.

Example of a graph that is not a DAG:

6
^
|
3->4
^  |
|  v
2<-5
^
|
1

This one is not acyclic because there is a cycle 2, 3, 4, 5, 2.

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The best websites of all time Updated 2025-07-16

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Multi-user:

Personal: Section "The best personal webpages of all time".

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Chemical element Updated 2025-07-16

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Chemical substance Updated 2025-07-16

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Chemist Updated 2025-07-16

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Differential equation Updated 2025-07-16

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Git tips / Linear history vs branching Updated 2025-07-16

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There are two ways to organize a project:

linear history
branched history: history with merge commits

Some people like merges, but they are ugly and stupid. Rebase instead and keep linear history.

Linear history:

5 master
|
4
|
3
|
2
|
1 first commit

Branched history:

7   master
|\
| \
6  \
|\  \
| |  |
3 4  5
| |  |
| /  /
|/  /
2  /
| /
1/  first commit

Here commits 6 and 7 are the so called "merge commits":

they have multiple parents:
- 6 has parents 3 and 4
- 7 has parents 5 and 6
they are useless and don't contain any real information

Which type of tree do you think will be easier to understand and maintain?

????

????????????

You may disconnect now if you still like branched history.

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Infinitesimal Updated 2025-07-16

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Just use limit instead, please. The French are particularly guilty of this.

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Limit (mathematics) Updated 2025-07-16

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The fundamental concept of calculus!

The reason why the epsilon delta definition is so venerated is that it fits directly into well known methods of the formalization of mathematics, making the notion completely precise.

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Cold Spring Harbor Laboratory Updated 2025-07-16

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A hot hot place.

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Git tips / Oh, but there are 2 trees: local and remote Updated 2025-07-16

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Oh but there are usually 2 trees: local and remote.

So you also have to learn how to observe and modify and sync with the remote tree!

But basically: