Posts Tagged ‘dvcs’

Mercurial Bookmarks Revisited – Part I

Bookmarks is an extension to the Mercurial SCM, which adds git-like branches to Mercurial. The extension is distributed together with Mercurial.
Recently the extension has received a major update. Time to look back.

This is a series of blogposts that consists of three parts:

(1) Part I: History of Bookmarks
(2) Part II: Daily Bookmarking
(3) Part III: Pushable Bookmarks

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Writing a hg to subversion gate

Using a decentralized version control system (DVCS) like Mercurial (hg) or Git as a client for Subversion is very common. With the unique features of a DVCS a developer can have both the features of offline development and local branching while still being able to push to a subversion server. This approach is often used in environments in which subversion is the given version control system. While the approach of using this bi-directional push and pull mechanism, provided by git-svn or hgsubversion, works perfectly for one developer, it has limitations working in a team using the usual DVCS push and pull concepts.

The following article will outline the current limitations of bi-directional dvcs to subversion bridges and shows a simple approach to implement a solution for a certain instance of the problem.

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hg-scm.org

For those of you, who didn’t notice so far, in the last 6 month we worked on a more userfriendly and accessible page than the current mercurial website. Three weeks ago we launched hg-scm.org which is quite similar to git-scm.org. I hope you enjoy it

git2svn, a little bit of git voodoo.

Interacting between git and subversion is quite common. The git command git-svn can be used to import existing subversion repositories into git and commit synchronize commits between two repositories. While importing a subversion repository into git is common, importing an git repository into subversion is quite unusual. There are various tools to do so, but most of them require direct access to the svn repository. In fact it is possible to use git-svn to get that job done. Frankly it requires some git voodoo and knowledge of the graft-feature. We’ll do a sample import using grafts, but before we start, we’ll explain the theory behind the import.
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Merge vs. Rebase – A deep dive into the mysteries of revision control

I remember the days when I started learning Git about two years ago. I crawled through all the available commands and read the man pages what they are for and I remember when I stumbled over rebase and stuck. After figuring out what it actually does, I start loving it, but didn’t understand it’s dangerousness until someday I somehow got duplicated commits after pulling from another repository. So let me explain what goes wrong and why merge and rebase are often misunderstood. I’ll also present a list of golden-rules about their usage. Before we start with explaining both commands, I would like to give you one of the most important rules, in case you don’t want to read the complete article.

Never rebase branches or trees that you pulled. Only rebase local branches.

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Mercurial bookmarks

Please note that this blog post is outdated. please refer to the mercurial help for more information about bookmarks.

A few month ago, Matt Mackall the maintainer of the Mercurial version control system, came up with the idea to implement so called bookmarks for mercurial.
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GIT vs. SVN: 2:0

Again, git vs. SVN. Last time, it was big win for git. And guess what, git will strike again.

I mean nobody is perfect (expect Linus, but there is just one – as he mentioned once), so we actually fail writing bugfree code. Therefore we end up sitting in front of a huge code base trying to figure out what’s wrong. Thanks to our agile development process we usually end up fixing code we are not into.

So the facts:

  • We don’t know the code
  • We don’t have a clue where to search
  • We are lazy

bisect
Okay, if we drop 1. and 2. we still have to find out what went wrong. So as we tend to get our evening beer fast and don’t want to waste time, we use git bisect to find out when the problem was introduced.

Assume following commit history:

a –> a’ (bug introduced) –> b –> a” –> c

When we bisect the problem, we will end up doing a quick search on the commits, marking buggy commits/trees bad and those that work fine good. This means, we mark c as good, then git will take us to a. We mark that commit as good, which will git move to b. If we mark b bad, git knows that a’ must introduce the bug. Than just view the diff and you might know where to find the bad code and how to fix it.

Well, as long nobody trashed the history with their ‘fixed a hundred bugs’ commits, containing like thousends of unrelated changes. In those cases, just bisect your collegue. git vs. SVN: 2:0

take it with humour

GIT vs. SVN: 1 : 0

I used git for the last 6 month in a big project. The project itself is not maintained
in git but in subversion as this is what developers know and what project leaders like to use
for several reasons.

In fact it’s not a bad idea to actually use subversion as version control system, particularly if
the developer are used to it. Well, I don’t care about that. Thanks to git-svn I could use
git as my subversion frontend. For sure, the distributed architecture of git didn’t help me that much when it comes to exchanging changes as I was the only developer using git.

But thanks to the repository format and git rich featureset, I found myself using git in a
much more productive way than people could use subversion.

Pickaxe:
What I really love is pickaxe. You can use that feature by passing -S to git log causing the log
to search for the string in the commit history and display all the commits that contain these changes.
Actually one of our developers had a problem with a blur event in the java script code, causing
all forms in the script to lose their focus all the time. He was just searching for the point all the
time as going through the commit messages was obviously too much time consuming (with about 100 commits per day). To make a long story short: I’m really a Javascript dumbass, but I just picked the
latest commits having a blur in their name with git log -Sblur and I found 2 promising commits. Showing him the commits actually solved the problem. He just missed one point in the thousands lines
of Javascript containing the blur event that caused the problems. Okay so here are the statistics for that event: Subversion with incremental search, but Javascript knowledge: 3hours. Git without any knowledige and a lazy person using it: 10mins. GIT vs. SVN: 1:0

Experimental PHP 5.3 Tree

Approaching the 5.3 release of PHP, a lot of features were introduced
and discussed at the internals mailinglist. This includes closures, traits
and various other patches. Some of these patches are on hold and not yet
applied. Therefore only a few people can take a look at the new features. Particularly because they scare patching PHP themselves or they run into troubles while patching. To make those patches available for a wider audience
I start maintaining a PHP 5.3-exp branch containing experimental features and
patches.

Who is the audience:

  • (Core) Developers that don’t want to maintain their own patch series
  • Developers that want to discuss recent proposals at the mailinglist
  • PHP lovers, that want to keep up-to-date

The 5.3-exp branch is available at:

http://git.experimentalworks.net/php-exp.git

Latest tarballs are available at:

http://git.experimentalworks.net/php-exp.git

Please notice that experimental patches are untested and therefor can cause
problems. Also notice that I cannot guarantee that the patches run under every
platform supported by PHP. The patchset is tested under a recent Ubuntu Linux
system with latest re2c and librarys from the Ubuntu repositories.

Comments are welcome

I love you, INDEX

Okay, there wasn’t a blog entry on git for quite a while, but well, here it is. This time about the incredible INDEX mechanism and git add -i. (more…)