About Iceberg design

Hi,

I'll write down some of the reasons of the project's design, like that I can afterwards copy paste it in the wiki :).

First, this design did not came up from an egg. We worked on it for about two months. And it is thought to be backwards compatible and manage lots of metacello particularities. It may have things that are perfectible, sure, so let's discuss it.

One of the main problems we saw in metacello, and that Iceberg inherited, was the "source subdirectory" thing. This source directory had to be specified in the CLIENT, meaning that every time we clone a repository we should know by heart the directory chose by its developer. Moreover, we lack a standard way to do it, so everybody does as he feels (root directory, src, source, repository, mc....).

This has some bad consequences:
 - once a repository is referenced by some other project, it is more
complicated to change its source directory. Imagine that tomorrow we set as standard that all git repos should have the code in src. Then voyage should change. And all its clients too.
 - Making a typo in the code subdirectory means sometimes super ugly errors from metacello that are difficult to debug and understand (e.g., "Cannot resolve BaselineOfMetacello WTF")

Moreover, there was another problem that people started stumbling on: the fact that iceberg got confused sometimes thinking that an empty project was in filetree (to keep backwards compatibility with projects without a .properties).

So we decided that for this release we wanted to revert a bit that
situation. Think object: let's put the meta-data used to interpret a
project's structure inside the project itself.
The idea is that:

 - each project should contain both a .project and a .properties file. The first can contain arbitrary project meta-data (such as the source directory). The second contains the cypress properties, which are needed to correctly interpret the code inside the source directory.
 - a project without a .project file is an old project and cannot be
interpreted, because we don't know the source directory
 - a project without a .properties file is an old project and is by default transformed in a project with a #filetree properties file
 - an old project cloned from iceberg detects the missing .project file and gives the user the opportunity to declare it (and then commit it explicitly)
 - an old project cloned and loaded from a Metacello expression defining a source directory will honnor the source directory defined in the Metacello expression (for backwards compatibility, and we have ~500 tests about this).

# About defaults values / forcing the user to define a project

First, notice that even when the repositories you load are just marked as "dirty".
This is because in memory we add a project to your repository. But you're not forced to commit it.Actually, you can still load packages and baselines from that repository without committing.

This is in line with Iceberg's "explicitness". We try to not do any
destructive operation without asking the user first (that's why we have several preview windows for pushing, pulling, checkout, merge..., and why
contrastingly with monticello we show the committed changes on the commit window...). So, instead of transparently "adding the file" we have decided to modify the project in memory and let the user the responsibility to commit that file.

If there's a drawback, is that the repository is marked as dirty. Which is a bit noisy, yes, but still I think it's not so bad compared with the previous drawbacks.
To solve this, we could have some default values, yes, and only mark it as dirty if the project does not follow the default value.
This could work, but right now all projects use different names for their source directories.
So the question is, what would be a good default? I'd like to use 'src' since this is short, well known and less alien (all these in the sense that we do not lose anything and we have a lot to gain by using it). However, not much repositories use 'src' so it will still produce a lot of "noise"...

But still! Committing that file is a one-time operation. Once people fix their repositories adding the project meta-data, you will not see them dirty anymore. So we can see this as a transition noise too...

Of course, new ideas are welcome. I'll let Pablo and Esteban add their points of view on this too.
Guille
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