Merge pull request #13296 from lujun9972/add-MjAxOTA0MTUgR2V0dGluZyBzdGFydGVkIHdpdGggTWVyY3VyaWFsIGZvciB2ZXJzaW9uIGNvbnRyb2wubWQK

选题: 20190415 Getting started with Mercurial for version control

sources/tech/20190415 Getting started with Mercurial for version control.md

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+[#]: collector: (lujun9972)
+[#]: translator: ( )
+[#]: reviewer: ( )
+[#]: publisher: ( )
+[#]: url: ( )
+[#]: subject: (Getting started with Mercurial for version control)
+[#]: via: (https://opensource.com/article/19/4/getting-started-mercurial)
+[#]: author: (Moshe Zadka (Community Moderator) https://opensource.com/users/moshez)
+
+Getting started with Mercurial for version control
+======
+Learn the basics of Mercurial, a distributed version control system
+written in Python.
+![][1]
+
+[Mercurial][2] is a distributed version control system written in Python. Because it's written in a high-level language, you can write a Mercurial extension with a few Python functions.
+
+There are several ways to install Mercurial, which are explained in the [official documentation][3]. My favorite one is not there: using **pip**. This is the most amenable way to develop local extensions!
+
+For now, Mercurial only supports Python 2.7, so you will need to create a Python 2.7 virtual environment:
+
+
+```
+python2 -m virtualenv mercurial-env
+./mercurial-env/bin/pip install mercurial
+```
+
+To have a short command, and to satisfy everyone's insatiable need for chemistry-based humor, the command is called **hg**.
+
+
+```
+$ source mercurial-env/bin/activate
+(mercurial-env)$ mkdir test-dir
+(mercurial-env)$ cd test-dir
+(mercurial-env)$ hg init
+(mercurial-env)$ hg status
+(mercurial-env)$
+```
+
+The status is empty since you do not have any files. Add a couple of files:
+
+
+```
+(mercurial-env)$ echo 1 > one
+(mercurial-env)$ echo 2 > two
+(mercurial-env)$ hg status
+? one
+? two
+(mercurial-env)$ hg addremove
+adding one
+adding two
+(mercurial-env)$ hg commit -m 'Adding stuff'
+(mercurial-env)$ hg log
+changeset: 0:1f1befb5d1e9
+tag: tip
+user: Moshe Zadka <[moshez@zadka.club][4]>
+date: Fri Mar 29 12:42:43 2019 -0700
+summary: Adding stuff
+```
+
+The **addremove** command is useful: it adds any new files that are not ignored to the list of managed files and removes any files that have been removed.
+
+As I mentioned, Mercurial extensions are written in Python—they are just regular Python modules.
+
+This is an example of a short Mercurial extension:
+
+
+```
+from mercurial import registrar
+from mercurial.i18n import _
+
+cmdtable = {}
+command = registrar.command(cmdtable)
+
+@command('say-hello',
+[('w', 'whom', '', _('Whom to greet'))])
+def say_hello(ui, repo, **opts):
+ui.write("hello ", opts['whom'], "\n")
+```
+
+A simple way to test it is to put it in a file in the virtual environment manually:
+
+
+```
+`$ vi ../mercurial-env/lib/python2.7/site-packages/hello_ext.py`
+```
+
+Then you need to _enable_ the extension. You can start by enabling it only in the current repository:
+
+
+```
+$ cat >> .hg/hgrc
+[extensions]
+hello_ext =
+```
+
+Now, a greeting is possible:
+
+
+```
+(mercurial-env)$ hg say-hello --whom world
+hello world
+```
+
+Most extensions will do more useful stuff—possibly even things to do with Mercurial. The **repo** object is a **mercurial.hg.repository** object.
+
+Refer to the [official documentation][5] for more about Mercurial's API. And visit the [official repo][6] for more examples and inspiration.
+
+--------------------------------------------------------------------------------
+
+via: https://opensource.com/article/19/4/getting-started-mercurial
+
+作者：[Moshe Zadka (Community Moderator)][a]
+选题：[lujun9972][b]
+译者：[译者ID](https://github.com/译者ID)
+校对：[校对者ID](https://github.com/校对者ID)
+
+本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
+
+[a]: https://opensource.com/users/moshez
+[b]: https://github.com/lujun9972
+[1]: https://opensource.com/sites/default/files/styles/image-full-size/public/lead-images/rh_003499_01_cloud21x_cc.png?itok=5UwC92dO
+[2]: https://www.mercurial-scm.org/
+[3]: https://www.mercurial-scm.org/wiki/UnixInstall
+[4]: mailto:moshez@zadka.club
+[5]: https://www.mercurial-scm.org/wiki/MercurialApi#Repositories
+[6]: https://www.mercurial-scm.org/repo/hg/file/tip/hgext