Re: [jgit-dev] Should FS become singleton-like?

[Shawn Pearce <spearce@xxxxxxxxxxx>]

The reason we were pushing FS down into APIs like Repository and its
dependencies is to allow a single JGit process to concurrently open
repositories on different drives, which may have different filesystem
semantics. On Windows this can be as simple as a repository under C:\
vs. a repository in your Cygwin home directory, also under C:\.

On Sat, Dec 30, 2017 at 4:57 AM, Marc Strapetz
<marc.strapetz@xxxxxxxxxxx> wrote:
> I've just uploaded another FS-related patch [1] which is addressing problems
> with LockFile (which became FS-dependent in version 4.5). I understand that
> most developers didn't fall in love with the configurable FS-approach
> started back in 2010: the idea was to not assume a single, auto-detectable
> Git installation with a single system Git config, but to allow using a
> custom (and possibly portable) Git installation and its system config by
> using a custom FS implementation.
>
> There are still 28 usages of FS.DETECTED in core org.eclipse.jgit production
> code. Some of them are just default values for already FS-aware methods,
> other usages are in central places, like:
>
> FileSnapshot.save(): FS.lastModified()
>
> or
>
> FileUtils: FS.exists(), FS.retryFailedLockFileCommit(), FS.relativize(), ...
>
> I guess similar as for FS.createNewFile() it could happen that their
> implementations will become dependent on the system Git config and then new
> problems will arise. Hence, my question:
>
> Should FS become "singleton-like", defaulting to FS.DETECTED, but with an
> additional setter so it can be (re)configured? I.e. something like:
>
> class FS {
>         private FS instance = detect();
>
>         public FS getInstance() {
>                 return instance;
>         }
>
>         public void setInstance(FS instance) {
>                 this.instance = instance;
>         }
>
>         ...
> }
>
> This will still allow to use custom Git installations and even change them
> during a program run; just not to use multiple Git installations
> concurrently. It would allow to drop lots of FS parameters and fields and
> help to simplify API somewhat. So something which could be done for version
> 5?
>
> [1] https://git.eclipse.org/r/#/c/114826/
>
> -Marc
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