The local manifest
Creating a local manifest allows you to customize the list of repositories on your copy of the source code by overriding the official manifest. In this way you can add, remove, or replace source code in the official manifest with your own. By pointing to new git repositories, (which need not even reside on the github site,) you can continue to synchronize with the repo sync command just as you would before. Only now, not only are official updates pulled from the regular manifest, but the remote git repositories specified in your manifest will also be checked, and new updates pulled to your source code.
Overriding the manifest
To override the contents of manifest.xml, you will need to write (or borrow) a plaintext XML file that defines the repos you want to pull from. There are two ways you can do this. The old deprecated way is to create a local_manifest.xml in the .repo directory. The new way (available in repo versions >= 1.19) is to create a folder called local_manifests and put that inside the .repo directory, then put your XML inside that directory. You can place as many override files in .repo/local_manifests as you like and repo will pick them up during the next sync. You can call the files anything you like as long as they end in .xml.
An example
Take a look at the following local_manifest.xml file. Then we'll discuss how it works.
<?xml version="1.0" encoding="UTF-8"?>
<manifest>
<remote name="omap" fetch="git://git.omapzoom.org/" />
<remove-project name="CyanogenMod/android_hardware_ti_omap3" />
<project path="hardware/ti/omap3" name="repo/android/hardware/ti/omap3" remote="omap" revision="jellybean"/>
</manifest>
The first two lines containing <?xml version="1.0" encoding="UTF-8"?> and <manifest> are standard, as is the last line, which contains </manifest>.
Next, a remote for git is declared and given the name "omap". (If you're not familiar with the concept of a remote in git, it essentially refers to a place (and method) for accessing a git repository. See here for more info.) In this case, omapzoom.org is a site that contains special up-to-date repositories for Texas Instrument's OMAP platform.
這個name有兩個用途：第一是在manifest.xml中讓每個project可以指定remote是誰；第二是這個name會作為屬於該remote的每個git project中的remote的名字，所以這個remote的名字就可以在git fetch的時候來使用。
此外注意這個remote中的fetch屬性，有的時候會看到定義成“..”。這表示是repo init的時候，指定的URL的上一層。比如repo init -u git://a.com/b，那么此時fetch為..的話就表示fetch的值是git://a.com。這個fetch其實是最終去git fetch每一個git project的時候的一個前綴。最終和git project中的name屬性的值拼在一起，成為最終git fetch的target。
找一個manifest.xml來看一遍會體會更深。包括還有如default element，指定default value，也很常用。
完整的manifest.xml的語法在這里：http://git-repo.googlecode.com/git-history/v1.8.1/docs/manifest-format.txt
The next line removes a project (the one at http://www.github.com/cyanogenmod/android_hardware_ti_omap3) declared in the original manifest.xml. It will now no longer be synced with repo sync.
The next line defines a new project. It replaces the one that was removed (from github.com/cyanogenmod) with one from Texas Instruments, using the "omap" remote that was defined above.
When adding a new project that replaces an existing project, you should always remove that project before defining the replacement. However, not every new project need replace an existing cyanogenmod project. You can also simply add a brand-new project to the source code, such as when you want to add your own app to the build.
Note that when adding new projects, there are at least three parts defined:
remote -- the name of the remote. this can be one that was defined in either the regular manifest or local_manifest.xml.
name -- the name of the git project-- for github it has the format account_name/project_name.
path -- where the git repository should go in your local copy of the source code.
revision -- (OPTIONAL) which branch or tag to use in the repository.
After adding .repo/local_manifests/your_file.xml, you should be able to repo sync and the source code should be updated accordingly.
Local Sources
To add local git repositories use something like fetch="file:///path/to/source"
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Intro: Adding a new app to the build
So after completing a build, people have been asking how to add their own app(s) to the CyanogenMod .zip file.
The "easy" way-- Add it to the zip manually
One way to do this is to simply add the .apk into the .zip and then edit the recovery installation script (written in a simple scripting language called "edify") to copy the file from the .zip to the device.
The "right" way: Make a part of the build repository so it auto-builds
Add app source to /packages/apps
You can do this manually, or you can do it via the .repo/local_manifests/*.xml（參考上面的講解）. If you do it this way, a repo sync will update the source to your app from whatever git repository you name in the local manifest. It's pretty easy to use, and allows you to override/replace/add/remove any official CM repository with one or more of your own.
Determine the name of the project from Android.mk
Regardless of how you put the source in packages/apps/, assuming that the source for the app has an Android.mk Makefile, you can get it to automatically build and install the resulting file in your $OUT directory (and thus your .zip) by simply determining the name of the project, which is typically defined in Android.mk with this:
LOCAL_PACKAGE_NAME := PackageName
以上的做完了，你的APK就會出現在out目錄中。如果要進入到最終編譯出來的zip（用於recovery刷機）或是img（用於fastboot刷機），還需要做：
Add the project to device.mk (or whatever .mk) in the device folder
Then just add that project to be built in the /device/[MANUFACTURER]/[CODENAME]/device.mk file.
Example:
Let's look at the grouper device aka the Nexus 7. You want to find where the list of packages to build is for this device, in device/asus/grouper/device-common.mk.
Note:
For the nexus 7, the device-common.mk file is shared with the tilapia device (the Nexus 7 GSM version), so if you're building for another device that doesn't have device-common.mk, you'd probably make the edit to device.mk instead.
Now you have a choice. If PRODUCT_PACKAGES was previously defined, you can add a value like this:
PRODUCT_PACKAGES += MyPackageName
The += part means to append it to the list.
Or, if it's simpler, you can just add it to the end an existing PRODUCT_PACKAGES list of projects by appending a "\" to the last item and then adding MyPackageName at the end. Notice that you can't put any commented lines (ie, lines starting with #) or even blank lines in the list of items to be built.
So if the list looks like this...
PRODUCT_PACKAGES := \
lights.grouper \
audio.primary.grouper
...you'd add it to the end:
PRODUCT_PACKAGES := \
lights.grouper \
audio.primary.grouper \
MyPackage
If the source for your app does not have the Android.mk makefile stuff, you'll need to add it. You can use any of the existing packages in packages/apps as a model for what needs to be done to build your particular app.
See http://www.kandroid.org/ndk/docs/ANDROID-MK.html for official documentation on Android .mk files.