ChineseTutorialFirstChange

教程 - 生成第一个[变更]

完成了[:TutorialHistory:教程-历史] 的学习之后， 我们来到 my-hello [仓库]里面，就是我们在 [:TutorialClone:教程-克隆]中 [克隆] 得到的。

在 ["Mercurial"] 开发实践中一个好的做法是把每个变更隔离在各自的[:Repository:仓库]里。这样可以避免把不相关的代码混杂起来， 并且便于一个接一个的测试每一部分工作。我们现在就开始采用这一模式。

我们的目标很简单，让“hello, world”程序打印另外一行输出。 首先， 我们给这个小项目创建一个新的仓库叫做 my-hello-new-output，方法是对my-hello做克隆。

$ cd ..
$ hg clone my-hello my-hello-new-output

这一次， 克隆命令如果成功将不会打印任何输出。

注: 注意我们给新的 [:Repository:仓库] 命名了一个描述性 的名字，基本上是说明这个[:Repository:仓库]的目的。 在["Mercurial"]里面给一个[:Repository:仓库]创建[克隆]很方便，我们会很快的积攒起很多稍微不同的仓库。如果我们不给他们描述性的命名， 很快就会没法分辨它们。

现在可以在新的仓库里面进行修改了 。 我们进入[:WorkingDirectory:工作目录]，使用我们喜欢的编辑软件修改源文件。

$ cd my-hello-new-output
$ vi hello.c

• hello.c 的内容原来是：

/*
 * hello.c
 *
 * Placed in the public domain by Bryan O'Sullivan
 *
 * This program is not covered by patents in the United States or other
 * countries.
 */

#include <stdio.h>

int main(int argc, char **argv)
{
        printf("hello, world!\n");
        return 0;
}

我们要修改 main 让它再多打印一行输出：

(...)

int main(int argc, char **argv)
{
        printf("hello, world!\n");
        printf("sure am glad I'm using Mercurial!\n");
        return 0;
}

完成之后退出我们喜欢的编辑器，任务完成。 有了刚才的修改我们就可以创建一个[变更集]。

可是万一我们背别的事情打扰，在创建变更集之后忘记了它里面有哪些变更，怎么办呢？ 这时候我们要用到status命令。

$ hg status
M hello.c

输出很简短。总之以 M 开头的行意思就是hello.c文件修改过了，那么我们的变更已经可以加入一个变更集了。

使用 diff 命令我们可以检查文件实际的改变：

$ hg diff
diff -r 82e55d328c8c hello.c
--- a/hello.c   Fri Aug 26 01:21:28 2005 -0700
+++ b/hello.c   Fri Sep 30 10:27:47 2005 +0800
@@ -12,5 +12,6 @@
 int main(int argc, char **argv)
 {
        printf("hello, world!\n");
+       printf("sure am glad I'm using Mercurial!\n");
        return 0;
 }

In case we wish to discard our changes and start over, we may use the revert command to restore the files to their unmodified state. Just make sure you know this is what you really want.

$ hg revert

The act of creating a ChangeSet is called ["Commit"]ting it. We perform a ["Commit"] using the commit command:

$ hg commit

This drops us into an editor, and presents us with a few cryptic lines of text.

Note: The default editor is vi. This can be changed using the EDITOR or HGEDITOR environment variables. Also, the manifest hash might be different, depending on how you typed and saved the file.

(empty line)
HG: manifest hash 14595beb70bcfb74bf227437d70c38878421c944
HG: changed hello.c

The first line is empty and the lines that follow identify the files that will go into this ChangeSet.

To ["Commit"] the ChangeSet, we must describe the reason for it. This is usually called a ChangeSet comment. Let's type something like this:

Express great joy at existence of Mercurial
HG: manifest hash 14595beb70bcfb74bf227437d70c38878421c944
HG: changed hello.c

Next, we save the test and quit the editor, and, if all goes well, the commit command will exit and prints no output. If you quit the editor without saving the text, commit will abort the operation, so you may change your mind before committing.

Let's see what the status command will tell us now?

$ hg status

Nothing! Our change has been ["Commit"]ted to a ChangeSet, so there's no modified file in need of a commit. Our ["Tip"] now matches our working directory contents.

We can now examine the change history for our new work:

$ hg log
changeset:   2:a58809af174d
tag:         tip
user:        mpm@selenic.com
date:        Fri Aug 26 01:26:28 2005 -0700
summary:     Express great joy at existence of Mercurial

(...)

There it is! We've ["Commit"]ted a ChangeSet.

Note: The user, date, and ChangeSetID will of course vary.

As we discussed in TutorialClone, the new ChangeSet only exists in this repository. This is a critical part of the way ["Mercurial"] works.

To share changes, we must continue to ChineseTutorialShareChange.