Re: yet another Ada web site?

["Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de>]

On 2022-10-14 13:19, Stephen Leake wrote:
> "Dmitry A. Kazakov" <mailbox@dmitry-kazakov.de> writes:
> 
>> On 2022-10-14 10:41, Fabien Chouteau wrote:
>>> On Thursday, October 13, 2022 at 8:58:20 AM UTC+2, Dmitry A. Kazakov wrote:
>>>> It seems so. Multiple versions at once are not supported. E.g. when you
>>>> are working on two projects both dependent on different versions of
>>>> another project:
>>>>
>>>> B -> A.1
>>>> C -> A.2
>>> Yes of course, different crates can depend on different version of
>>> the same crate.
>>
>> It is about whether both A's can be installed and coexist on the same
>> machine.
> 
> In Alire, "installed" means "checked out the source code into a local
> directory".
> 
> If A depends on a system library that is a shared object file, and those
> are different versions, then it depends on the OS; Debian can handle
> this nicely, Windows only via separate directories and search paths.
> 
> 
>>>> Or even the same project, e.g. when doing some migration from one
>>>> version to another.
>>> Not sure how you would do that? Link two different version of the
>>> same library in an executable? That's not going to work.
>>
>> Same as above. You have B.1 -> A.1 and B.* -> A.2. You want to install
>> both A.1 and A.2 and work on B.* while checking on B.1.
> 
> And the solution is the same as well.
> 
>> In the long gone time of common sense, a project code management
>> system would use a virtual file system and map different parts of the
>> projects graph onto a structure of folders arranged by versions.
> 
> What prevents that now?

Nothing except that it is to be done manually. Why not download a source 
archive and bother with anything? It is Turing-complete, after all... (:-))

The advantage of a file system is that developing image will be 
automated and consistent. And you would not need to move any files 
physically. Alire is extremely slow because it must pull all files [and 
then compile them on top of that].

Furthermore, a virtual file system shares duplicates of the same version 
of same file. When you work with naked Git you must have as many copies 
as you have projects. Same applies to virtual machines and dockers. It 
is a huge overhead for nothing.

Moreover, a virtual file system is instant so long you do not access a 
file for read or write. Which is the case for gprbuild, make and other 
tools which use timestamps and then never look into files.

With a virtual file system you can automatically check in all files on 
closing if it was open for write and never worry about command-line mess 
or plug-ins. Any tool will work out of the box.

-- 
Regards,
Dmitry A. Kazakov
http://www.dmitry-kazakov.de