Working on Wednesday #9 : Mercurial
11 Aug 2011I'm feeling like I'm getting more and more behind schedule for what I intended to do at first. I still haven't tried Rails more than that and have gone on different learning side projects.
_I've been reading the _Mercurial : Definite Guide the past few days to get a correct grasp of the soft.
I've been using Mercurial for the pas two years, but through a GUI and without using any "advanced" features. I never branched a project, and always worked alone.
Commands
Now that I'm working on a Linux machine every day, I can use hg through the command line.
hg commit -Am "commit message" is the same as hg addremove; hg commit -m "commit message".
hg rollback will remove the last local commit. Useful if you forgot files in the commit, or if you inserted a typo in your commit message
hg revert can revert a file or set of files to the state they were at the last commit. This can also cancel a hg add or hg remove
hg backout can "forget" a commit in the history. It will not really forget the commit (ie. will not let you alter the history). Instead, it will create a new commit where the specified changeset is removed (through a merge). It can easily backout the tip, but may involve more merge work if we want to backout an old changeset.
Automation
Also, I've learned about two great tools of Mercurial.
hg bisect let you isolate a specified commit in your history where you introduced a specific bug. You write a piece of code that, given a changeset, returns true or false based on the bug presence, and hg bisect will cleverly scan the history to find the revision that introduced the bug.
hooks where also very interesting. One can script automatic command on specific hg command like commit, pull, push. Or even before those commande to refuse the command if something does not work as expected.
The classical examples where running a build process after a commit, refusing a commit if no bug id where specified, or if the tests didn't pass. Another use case would be to push changes to a remote server on commit.
Git
Why am I learning Mercurial while all the cool guys are using git ?
Well, I've read a lot of papers comparing hg to git. What I've read the more is that git is an awesome toolbox that lets you do whatever you want with your version control, through its 100+ tools.
On the other hand, Mercurial is far easier to learn and has built-in command for the day to day work. As I was already quite familiar with Mercurial, I stick with it, but know that I'll learn git also eventually.
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