doc update

Author: merlynomsft

docs/localpackages_buildconfig.md

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+## Usage examples
+
+node make.js build --includeLocalPackagesBuildConfig
+node make.js build --includeLocalPackagesBuildConfig --task MavenV4
+
+## What does specifing --includeLocalPackagesBuildConfig do?
+
+It produces a new LocalPackages config, which updates several package.json references to point to local files.
+
+A single version is used for all LocalPackages, stored in [gitroot]\globalversion.txt.  globalversion.txt is only created if "—includeLocalPackagesBuildConfig" is specified.
+
+globalversion.txt (if present) is updated to avoid clashes with existing task versions.  The global version specified is use for tasks generated under LocalPackages build.config.  The version number is [major from task].[sprint].[patch]
+
+This hybrid approach is transitionary.  In the future, all build configs (including the default) will use the global version.
+
+## sub-tree
+
+Subtrees were added to pull in modules from other repos
+
+git clone https://github.com/microsoft/azure-pipelines-tasks  
+
+
+# add (one time)
+git remote add -f azure-pipelines-task-lib https://github.com/microsoft/azure-pipelines-task-lib
+git subtree add --prefix task-lib azure-pipelines-task-lib master --squash
+
+git remote add -f azure-pipelines-tasks-common-packages https://github.com/microsoft/azure-pipelines-tasks-common-packages
+git subtree add --prefix tasks-common azure-pipelines-tasks-common-packages main --squash
+
+# pull
+git subtree pull --prefix task-lib azure-pipelines-task-lib master --squash
+git subtree pull --prefix tasks-common azure-pipelines-tasks-common-packages main --squash
+