For all details and references of the project one can visit darcs-GSoC-2014-History-Reordering-Performance-and-Features.

martes, 29 de julio de 2014

Other Week (21-26 July)

Good news!

I almost finish to implement the option minimize-context for the command darcs send, I say almost because making some examples I find out that somethings could go wrong. But before entering in that, I will comment a little the main the test that without minimize-context doesn't work and with the option passes(when the implementation is ready the most likely is I will upload the example and some more in ExamplesRepos), and some "tentatives options" for darcs send that I think could be useful.

So, the minimal example:

Suppose we have repositories $r_1$, $r_2$ and $r_3$; $r_2$ a direct clone of $r_1$ where
originally $r_1$ has only one patch, 

$r_1$,$r_2$ $=$ $p_0$

now, we add a patch with a new file in $r_1$ and make a clone, $r_3$ which leave the repositories like this,

$r_1$,$r_3$ $=$ $p_0$ $p_1$

Suppose that we make a modification in the file that add $p_0$ and make a patch $p'_0$ in $r_1$ and we send a bundle (with darcs send) to $r_2$ and $r_3$. What ends up happening is what one imagine,
the bundle can be applied to $r_3$ but not to $r_2$, this because the bundle has de following "shape":

Some message

patch [Some hash]
Author: ...
Date: ...
  * [The modification to $p_0$]

New patches:




Patch bundle hash: [Some hash]

and $r_2$ doesn't have the patch $p_1$ despite the fact that $p_1$ nothing has to do with $p'_0$. Using the option minimize-context the bundle is the same but the "Context" is:



and now there is no problem.

Now, I find out that reducing the context is not always the "best option" for send a bundle. Here I will expose something that could go wrong. Take for example the darcs-screened repository, in total has 11000~ patches, suppose we add a file and make a bundle (using minimize-context) with only the patch that make the add, the context then is empty. So, if we try to apply this bundle to, say the remote repository, this could never end...
What go wrong?; because the context is empty, making darcs apply [TheBundle] in some point try to merge the entire repository versus the "set" of patches to apply, this is very costly if we have 11000~ patches.

I write "best option" before because with my current solution is not always is better reduce the context, but the final idea is that always be the best option. So, I think is necessary to have some care for example in the last implementation if exist a tag, this tag is added to the context. This simple solution solves the problem and seems correct, on the other hand having more than 600~ or 1000~ patches without a tag seem a little extreme :)

Ending, I'm making some tests of two interesting options that came to mind:

. --last-deps=NUMBER
. --deps-from-tag=REGEXP

The first searches dependencies in the first N patches, and the second search since a given tag.

In conclusion, I'm still doubtful about how solve that problem. More if I have consider the two options. For the end of the week I hope have all this solved.

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