From 5c105d9f3fd086aff195d3849dcf847d6b0bd927 Mon Sep 17 00:00:00 2001
From: blogic <blogic@3c298f89-4303-0410-b956-a3cf2f4a3e73>
Date: Fri, 5 Oct 2012 10:12:53 +0000
Subject: branch Attitude Adjustment

git-svn-id: svn://svn.openwrt.org/openwrt/branches/attitude_adjustment@33625 3c298f89-4303-0410-b956-a3cf2f4a3e73
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+One of the biggest challenges to getting started with embedded devices is that you
+cannot just install a copy of Linux and expect to be able to compile a firmware.
+Even if you did remember to install a compiler and every development tool offered,
+you still would not have the basic set of tools needed to produce a firmware image.
+The embedded device represents an entirely new hardware platform, which is
+most of the time incompatible with the hardware on your development machine, so in a process called
+cross compiling you need to produce a new compiler capable of generating code for
+your embedded platform, and then use it to compile a basic Linux distribution to
+run on your device.
+
+The process of creating a cross compiler can be tricky, it is not something that is
+regularly attempted and so there is a certain amount of mystery and black magic
+associated with it. In many cases when you are dealing with embedded devices you will
+be provided with a binary copy of a compiler and basic libraries rather than
+instructions for creating your own -- it is a time saving step but at the same time
+often means you will be using a rather dated set of tools. Likewise, it is also common
+to be provided with a patched copy of the Linux kernel from the board or chip vendor,
+but this is also dated and it can be difficult to spot exactly what has been
+modified to make the kernel run on the embedded platform.
+
+\subsection{Building an image}
+
+OpenWrt takes a different approach to building a firmware; downloading, patching
+and compiling everything from scratch, including the cross compiler. To put it
+in simpler terms, OpenWrt does not contain any executables or even sources, it is an
+automated system for downloading the sources, patching them to work with the given
+platform and compiling them correctly for that platform. What this means is that
+just by changing the template, you can change any step in the process.
+
+As an example, if a new kernel is released, a simple change to one of the Makefiles
+will download the latest kernel, patch it to run on the embedded platform and produce
+a new firmware image -- there is no work to be done trying to track down an unmodified
+copy of the existing kernel to see what changes had been made, the patches are
+already provided and the process ends up almost completely transparent. This does not
+just apply to the kernel, but to anything included with OpenWrt -- It is this one
+simple understated concept which is what allows OpenWrt to stay on the bleeding edge
+with the latest compilers, latest kernels and latest applications.
+
+So let's take a look at OpenWrt and see how this all works.
+
+
+\subsubsection{Download OpenWrt}
+
+OpenWrt can be downloaded via subversion using the following command:
+
+\begin{Verbatim}
+$ svn checkout svn://svn.openwrt.org/openwrt/trunk openwrt-trunk
+\end{Verbatim}
+
+Additionally, there is a trac interface on \href{https://dev.openwrt.org/}{https://dev.openwrt.org/}
+which can be used to monitor svn commits and browse the source repository.
+
+
+\subsubsection{The directory structure}
+
+There are four key directories in the base:
+
+\begin{itemize}
+    \item \texttt{tools}
+    \item \texttt{toolchain}
+    \item \texttt{package}
+    \item \texttt{target}
+\end{itemize}
+
+\texttt{tools} and \texttt{toolchain} refer to common tools which will be
+used to build the firmware image, the compiler, and the C library.
+The result of this is three new directories, \texttt{build\_dir/host}, which is a temporary
+directory for building the target independent tools, \texttt{build\_dir/toolchain-\textit{<arch>}*}
+which is used for building the toolchain for a specific architecture, and
+\texttt{staging\_dir/toolchain-\textit{<arch>}*} where the resulting toolchain is installed.
+You will not need to do anything with the toolchain directory unless you intend to
+add a new version of one of the components above.
+
+\begin{itemize}
+    \item \texttt{build\_dir/host}
+    \item \texttt{build\_dir/toolchain-\textit{<arch>}*}
+\end{itemize}
+
+\texttt{package} is for exactly that -- packages. In an OpenWrt firmware, almost everything
+is an \texttt{.ipk}, a software package which can be added to the firmware to provide new
+features or removed to save space. Note that packages are also maintained outside of the main
+trunk and can be obtained from subversion using the package feeds system:
+
+\begin{Verbatim}
+$ ./scripts/feeds update
+\end{Verbatim}
+
+Those packages can be used to extend the functionality of the build system and need to be
+symlinked into the main trunk. Once you do that, the packages will show up in the menu for
+configuration. You would do something like this:
+
+\begin{Verbatim}
+$ ./scripts/feeds search nmap
+Search results in feed 'packages':
+nmap       Network exploration and/or security auditing utility
+
+$ ./scripts/feeds install nmap
+\end{Verbatim}
+
+To include all packages, issue the following command:
+
+\begin{Verbatim}
+$ make package/symlinks
+\end{Verbatim}
+
+\texttt{target} refers to the embedded platform, this contains items which are specific to
+a specific embedded platform. Of particular interest here is the "\texttt{target/linux}"
+directory which is broken down by platform \textit{<arch>} and contains the patches to the
+kernel, profile config, for a particular platform. There's also the "\texttt{target/image}" directory
+which describes how to package a firmware for a specific platform.
+
+Both the target and package steps will use the directory "\texttt{build\_dir/\textit{<arch>}}"
+as a temporary directory for compiling. Additionally, anything downloaded by the toolchain,
+target or package steps will be placed in the "\texttt{dl}" directory.
+
+\begin{itemize}
+    \item \texttt{build\_dir/\textit{<arch>}}
+    \item \texttt{dl}
+\end{itemize}
+
+\subsubsection{Building OpenWrt}
+
+While the OpenWrt build environment was intended mostly for developers, it also has to be
+simple enough that an inexperienced end user can easily build his or her own customized firmware.
+
+Running the command "\texttt{make menuconfig}" will bring up OpenWrt's configuration menu
+screen, through this menu you can select which platform you're targeting, which versions of
+the toolchain you want to use to build and what packages you want to install into the
+firmware image. Note that it will also check to make sure you have the basic dependencies for it
+to run correctly.  If that fails, you will need to install some more tools in your local environment
+before you can begin.
+
+Similar to the linux kernel config, almost every option has three choices,
+\texttt{y/m/n} which are represented as follows:
+
+\begin{itemize}
+    \item{\texttt{<*>} (pressing y)} \\
+        This will be included in the firmware image
+    \item{\texttt{<M>} (pressing m)} \\
+        This will be compiled but not included (for later install)
+    \item{\texttt{< >} (pressing n)} \\
+        This will not be compiled
+\end{itemize}
+
+After you've finished with the menu configuration, exit and when prompted, save your
+configuration changes.
+
+If you want, you can also modify the kernel config for the selected target system.
+simply run "\texttt{make kernel\_menuconfig}" and the build system will unpack the kernel sources
+(if necessary), run menuconfig inside of the kernel tree, and then copy the kernel config
+to \texttt{target/linux/\textit{<platform>}/config} so that it is preserved over
+"\texttt{make clean}" calls.
+
+To begin compiling the firmware, type "\texttt{make}". By default
+OpenWrt will only display a high level overview of the compile process and not each individual
+command.
+
+\subsubsection{Example:}
+
+\begin{Verbatim}
+make[2] toolchain/install
+make[3] -C toolchain install
+make[2] target/compile
+make[3] -C target compile
+make[4] -C target/utils prepare
+
+[...]
+\end{Verbatim}
+
+This makes it easier to monitor which step it's actually compiling and reduces the amount
+of noise caused by the compile output. To see the full output, run the command
+"\texttt{make V=99}".
+
+During the build process, buildroot will download all sources to the "\texttt{dl}"
+directory and will start patching and compiling them in the "\texttt{build\_dir/\textit{<arch>}}"
+directory. When finished, the resulting firmware will be in the "\texttt{bin}" directory
+and packages will be in the "\texttt{bin/packages}" directory.
+
+
+\subsection{Creating packages}
+
+One of the things that we've attempted to do with OpenWrt's template system is make it
+incredibly easy to port software to OpenWrt. If you look at a typical package directory
+in OpenWrt you'll find several things:
+
+\begin{itemize}
+    \item \texttt{package/\textit{<name>}/Makefile}
+    \item \texttt{package/\textit{<name>}/patches}
+    \item \texttt{package/\textit{<name>}/files}
+\end{itemize}
+
+The patches directory is optional and typically contains bug fixes or optimizations to
+reduce the size of the executable. The package makefile is the important item, provides
+the steps actually needed to download and compile the package.
+
+The files directory is also optional and typicall contains package specific startup scripts or default configuration files that can be used out of the box with OpenWrt.
+
+Looking at one of the package makefiles, you'd hardly recognize it as a makefile.
+Through what can only be described as blatant disregard and abuse of the traditional
+make format, the makefile has been transformed into an object oriented template which
+simplifies the entire ordeal.
+
+Here for example, is \texttt{package/bridge/Makefile}:
+
+\begin{Verbatim}[frame=single,numbers=left]
+
+include $(TOPDIR)/rules.mk
+
+PKG_NAME:=bridge
+PKG_VERSION:=1.0.6
+PKG_RELEASE:=1
+
+PKG_SOURCE:=bridge-utils-$(PKG_VERSION).tar.gz
+PKG_SOURCE_URL:=@SF/bridge
+PKG_MD5SUM:=9b7dc52656f5cbec846a7ba3299f73bd
+PKG_CAT:=zcat
+
+PKG_BUILD_DIR:=$(BUILD_DIR)/bridge-utils-$(PKG_VERSION)
+
+include $(INCLUDE_DIR)/package.mk
+
+define Package/bridge
+  SECTION:=net
+  CATEGORY:=Base system
+  TITLE:=Ethernet bridging configuration utility
+  URL:=http://bridge.sourceforge.net/
+endef
+
+define Package/bridge/description
+  Manage ethernet bridging: 
+  a way to connect networks together to form a larger network.
+endef
+
+define Build/Configure
+    $(call Build/Configure/Default, \
+        --with-linux-headers="$(LINUX_DIR)" \
+    )
+endef
+
+define Package/bridge/install
+    $(INSTALL_DIR) $(1)/usr/sbin
+    $(INSTALL_BIN) $(PKG_BUILD_DIR)/brctl/brctl $(1)/usr/sbin/
+endef
+
+$(eval $(call BuildPackage,bridge))
+\end{Verbatim}
+
+As you can see, there's not much work to be done; everything is hidden in other makefiles
+and abstracted to the point where you only need to specify a few variables.
+
+\begin{itemize}
+    \item \texttt{PKG\_NAME} \\
+        The name of the package, as seen via menuconfig and ipkg
+    \item \texttt{PKG\_VERSION} \\
+        The upstream version number that we are downloading
+    \item \texttt{PKG\_RELEASE} \\
+        The version of this package Makefile
+    \item \texttt{PKG\_SOURCE} \\
+        The filename of the original sources
+    \item \texttt{PKG\_SOURCE\_URL} \\
+        Where to download the sources from (no trailing slash), you can add multiple download sources by separating them with a \\ and a carriage return.
+    \item \texttt{PKG\_MD5SUM} \\
+        A checksum to validate the download
+    \item \texttt{PKG\_CAT} \\
+        How to decompress the sources (zcat, bzcat, unzip)
+    \item \texttt{PKG\_BUILD\_DIR} \\
+        Where to compile the package
+\end{itemize}
+
+The \texttt{PKG\_*} variables define where to download the package from;
+\texttt{@SF} is a special keyword for downloading packages from sourceforge. There is also
+another keyword of \texttt{@GNU} for grabbing GNU source releases. If any of the above mentionned download source fails, the OpenWrt mirrors will be used as source.
+
+The md5sum (if present) is used to verify the package was downloaded correctly and
+\texttt{PKG\_BUILD\_DIR} defines where to find the package after the sources are
+uncompressed into \texttt{\$(BUILD\_DIR)}.
+
+At the bottom of the file is where the real magic happens, "BuildPackage" is a macro
+set up by the earlier include statements. BuildPackage only takes one argument directly --
+the name of the package to be built, in this case "\texttt{bridge}". All other information
+is taken from the define blocks. This is a way of providing a level of verbosity, it's
+inherently clear what the contents of the \texttt{description} template in
+\texttt{Package/bridge} is, which wouldn't be the case if we passed this information
+directly as the Nth argument to \texttt{BuildPackage}.
+
+\texttt{BuildPackage} uses the following defines:
+
+\textbf{\texttt{Package/\textit{<name>}}:} \\
+    \texttt{\textit{<name>}} matches the argument passed to buildroot, this describes
+    the package the menuconfig and ipkg entries. Within \texttt{Package/\textit{<name>}}
+    you can define the following variables:
+
+    \begin{itemize}
+        \item \texttt{SECTION} \\
+            The section of package (currently unused)
+        \item \texttt{CATEGORY} \\
+            Which menu it appears in menuconfig: Network, Sound, Utilities, Multimedia ...
+        \item \texttt{TITLE} \\
+            A short description of the package
+        \item \texttt{URL} \\
+            Where to find the original software
+        \item \texttt{MAINTAINER} (optional) \\
+            Who to contact concerning the package
+        \item \texttt{DEPENDS} (optional) \\
+            Which packages must be built/installed before this package. To reference a dependency defined in the
+			same Makefile, use \textit{<dependency name>}. If defined as an external package, use 
+			\textit{+<dependency name>}. For a kernel version dependency use: \textit{@LINUX\_2\_<minor version>}
+		\item \texttt{BUILDONLY} (optional) \\
+			Set this option to 1 if you do NOT want your package to appear in menuconfig.
+			This is useful for packages which are only used as build dependencies.
+    \end{itemize}
+
+\textbf{\texttt{Package/\textit{<name>}/conffiles} (optional):} \\
+   A list of config files installed by this package, one file per line.
+
+\textbf{\texttt{Build/Prepare} (optional):} \\
+   A set of commands to unpack and patch the sources. You may safely leave this
+   undefined.
+
+\textbf{\texttt{Build/Configure} (optional):} \\
+   You can leave this undefined if the source doesn't use configure or has a
+   normal config script, otherwise you can put your own commands here or use
+   "\texttt{\$(call Build/Configure/Default,\textit{<first list of arguments, second list>})}" as above to
+   pass in additional arguments for a standard configure script. The first list of arguments will be passed
+   to the configure script like that: \texttt{--arg 1} \texttt{--arg 2}. The second list contains arguments that should be
+   defined before running the configure script such as autoconf or compiler specific variables.
+   
+   To make it easier to modify the configure command line, you can either extend or completely override the following variables:
+   \begin{itemize}
+     \item \texttt{CONFIGURE\_ARGS} \\
+	     Contains all command line arguments (format: \texttt{--arg 1} \texttt{--arg 2})
+     \item \texttt{CONFIGURE\_VARS} \\
+	     Contains all environment variables that are passed to ./configure (format: \texttt{NAME="value"})
+   \end{itemize}
+
+\textbf{\texttt{Build/Compile} (optional):} \\
+   How to compile the source; in most cases you should leave this undefined.
+   
+   As with \texttt{Build/Configure} there are two variables that allow you to override
+   the make command line environment variables and flags:
+   \begin{itemize}
+     \item \texttt{MAKE\_FLAGS} \\
+	   Contains all command line arguments (typically variable overrides like \texttt{NAME="value"}
+	 \item \texttt{MAKE\_VARS} \\
+	   Contains all environment variables that are passed to the make command
+   \end{itemize}
+
+\textbf{\texttt{Build/InstallDev} (optional):} \\
+	If your package provides a library that needs to be made available to other packages,
+	you can use the \texttt{Build/InstallDev} template to copy it into the staging directory
+	which is used to collect all files that other packages might depend on at build time.
+	When it is called by the build system, two parameters are passed to it. \texttt{\$(1)} points to
+	the regular staging dir, typically \texttt{staging\_dir/\textit{ARCH}}, while \texttt{\$(2)} points
+	to \texttt{staging\_dir/host}. The host staging dir is only used for binaries, which are
+	to be executed or linked against on the host and its \texttt{bin/} subdirectory is included
+	in the \texttt{PATH} which is passed down to the build system processes.
+	Please use \texttt{\$(1)} and \texttt{\$(2)} here instead of the build system variables
+	\texttt{\$(STAGING\_DIR)} and \texttt{\$(STAGING\_DIR\_HOST)}, because the build system behavior
+	when staging libraries might change in the future to include automatic uninstallation.
+
+\textbf{\texttt{Package/\textit{<name>}/install}:} \\
+   A set of commands to copy files out of the compiled source and into the ipkg
+   which is represented by the \texttt{\$(1)} directory. Note that there are currently
+   4 defined install macros:
+   \begin{itemize}
+       \item \texttt{INSTALL\_DIR} \\
+           install -d -m0755
+       \item \texttt{INSTALL\_BIN} \\
+           install -m0755
+       \item \texttt{INSTALL\_DATA} \\
+           install -m0644
+       \item \texttt{INSTALL\_CONF} \\
+           install -m0600
+   \end{itemize}
+
+The reason that some of the defines are prefixed by "\texttt{Package/\textit{<name>}}"
+and others are simply "\texttt{Build}" is because of the possibility of generating
+multiple packages from a single source. OpenWrt works under the assumption of one
+source per package Makefile, but you can split that source into as many packages as
+desired. Since you only need to compile the sources once, there's one global set of
+"\texttt{Build}" defines, but you can add as many "Package/<name>" defines as you want
+by adding extra calls to \texttt{BuildPackage} -- see the dropbear package for an example.
+
+After you have created your \texttt{package/\textit{<name>}/Makefile}, the new package
+will automatically show in the menu the next time you run "make menuconfig" and if selected
+will be built automatically the next time "\texttt{make}" is run.
+
+\subsection{Creating binary packages}
+
+You might want to create binary packages and include them in the resulting images as packages.
+To do so, you can use the following template, which basically sets to nothing the Configure and
+Compile templates.
+
+\begin{Verbatim}[frame=single,numbers=left]
+
+include $(TOPDIR)/rules.mk
+
+PKG_NAME:=binpkg
+PKG_VERSION:=1.0
+PKG_RELEASE:=1
+
+PKG_SOURCE:=binpkg-$(PKG_VERSION).tar.gz
+PKG_SOURCE_URL:=http://server
+PKG_MD5SUM:=9b7dc52656f5cbec846a7ba3299f73bd
+PKG_CAT:=zcat
+
+include $(INCLUDE_DIR)/package.mk
+
+define Package/binpkg
+  SECTION:=net
+  CATEGORY:=Network
+  TITLE:=Binary package
+endef
+
+define Package/bridge/description
+  Binary package
+endef
+
+define Build/Configure
+endef
+
+define Build/Compile
+endef
+
+define Package/bridge/install
+    $(INSTALL_DIR) $(1)/usr/sbin
+    $(INSTALL_BIN) $(PKG_BUILD_DIR)/* $(1)/usr/sbin/
+endef
+
+$(eval $(call BuildPackage,bridge))
+\end{Verbatim}
+
+Provided that the tarball which contains the binaries reflects the final
+directory layout (/usr, /lib ...), it becomes very easy to get your package
+look like one build from sources.
+
+Note that using the same technique, you can easily create binary pcakages
+for your proprietary kernel modules as well.
+
+\subsection{Creating kernel modules packages}
+
+The OpenWrt distribution makes the distinction between two kind of kernel modules, those coming along with the mainline kernel, and the others available as a separate project. We will see later that a common template is used for both of them.
+
+For kernel modules that are part of the mainline kernel source, the makefiles are located in \textit{package/kernel/modules/*.mk} and they appear under the section "Kernel modules"
+
+For external kernel modules, you can add them to the build system just like if they were software packages by defining a KernelPackage section in the package makefile.
+
+Here for instance the Makefile for the I2C subsytem kernel modules :
+
+\begin{Verbatim}[frame=single,numbers=left]
+
+I2CMENU:=I2C Bus
+
+define KernelPackage/i2c-core
+  TITLE:=I2C support
+  DESCRIPTION:=Kernel modules for i2c support
+  SUBMENU:=$(I2CMENU)
+  KCONFIG:=CONFIG_I2C_CORE CONFIG_I2C_DEV
+  FILES:=$(MODULES_DIR)/kernel/drivers/i2c/*.$(LINUX_KMOD_SUFFIX)
+  AUTOLOAD:=$(call AutoLoad,50,i2c-core i2c-dev)
+endef
+$(eval $(call KernelPackage,i2c-core))
+\end{Verbatim}
+
+To group kernel modules under a common description in menuconfig, you might want to define a \textit{<description>MENU} variable on top of the kernel modules makefile.
+
+\begin{itemize}
+    \item \texttt{TITLE} \\
+        The name of the module as seen via menuconfig
+    \item \texttt{DESCRIPTION} \\
+        The description as seen via help in menuconfig
+    \item \texttt{SUBMENU} \\
+        The sub menu under which this package will be seen
+    \item \texttt{KCONFIG} \\
+        Kernel configuration option dependency. For external modules, remove it.
+    \item \texttt{FILES} \\
+        Files you want to inlude to this kernel module package, separate with spaces.
+    \item \texttt{AUTOLOAD} \\
+        Modules that will be loaded automatically on boot, the order you write them is the order they would be loaded.
+\end{itemize}
+
+After you have created your \texttt{package/kernel/modules/\textit{<name>}.mk}, the new kernel modules package
+will automatically show in the menu under "Kernel modules" next time you run "make menuconfig" and if selected
+will be built automatically the next time "\texttt{make}" is run.
+
+\subsection{Conventions}
+
+There are a couple conventions to follow regarding packages:
+
+\begin{itemize}
+    \item \texttt{files}
+    \begin{enumerate}
+        \item configuration files follow the convention \\
+        \texttt{\textit{<name>}.conf}
+        \item init files follow the convention \\
+        \texttt{\textit{<name>}.init}
+    \end{enumerate}
+    \item \texttt{patches}
+    \begin{enumerate}
+        \item patches are numerically prefixed and named related to what they do
+    \end{enumerate}
+\end{itemize}
+
+\subsection{Troubleshooting}
+
+If you find your package doesn't show up in menuconfig, try the following command to
+see if you get the correct description:
+
+\begin{Verbatim}
+  TOPDIR=$PWD make -C package/<name> DUMP=1 V=99
+\end{Verbatim}
+
+If you're just having trouble getting your package to compile, there's a few
+shortcuts you can take. Instead of waiting for make to get to your package, you can
+run one of the following:
+
+\begin{itemize}
+    \item \texttt{make package/\textit{<name>}/clean V=99}
+    \item \texttt{make package/\textit{<name>}/install V=99}
+\end{itemize}
+
+Another nice trick is that if the source directory under \texttt{build\_dir/\textit{<arch>}}
+is newer than the package directory, it won't clobber it by unpacking the sources again.
+If you were working on a patch you could simply edit the sources under the
+\texttt{build\_dir/\textit{<arch>}/\textit{<source>}} directory and run the install command above,
+when satisfied, copy the patched sources elsewhere and diff them with the unpatched
+sources. A warning though - if you go modify anything under \texttt{package/\textit{<name>}}
+it will remove the old sources and unpack a fresh copy.
+
+Other useful targets include:
+
+\begin{itemize}
+    \item \texttt{make package/\textit{<name>}/prepare V=99}
+    \item \texttt{make package/\textit{<name>}/compile V=99}
+    \item \texttt{make package/\textit{<name>}/configure V=99}
+\end{itemize}
+
+
+\subsection{Using build environments}
+OpenWrt provides a means of building images for multiple configurations
+which can use multiple targets in one single checkout. These \emph{environments}
+store a copy of the .config file generated by \texttt{make menuconfig} and the contents
+of the \texttt{./files} folder.
+The script \texttt{./scripts/env} is used to manage these environments, it uses
+\texttt{git} (which needs to be installed on your system) as backend for version control.
+
+The command 
+\begin{Verbatim}
+  ./scripts/env help
+\end{Verbatim}
+produces a short help text with a list of commands.
+
+To create a new environment named \texttt{current}, run the following command
+\begin{Verbatim}
+  ./scripts/env new current
+\end{Verbatim}
+This will move your \texttt{.config} file and \texttt{./files} (if it exists) to
+the \texttt{env/} subdirectory and create symlinks in the base folder.
+
+After running make menuconfig or changing things in files/, your current state will
+differ from what has been saved before. To show these changes, use:
+\begin{Verbatim}
+  ./scripts/env diff
+\end{Verbatim}
+
+If you want to save these changes, run:
+\begin{Verbatim}
+  ./scripts/env save
+\end{Verbatim}
+If you want to revert your changes to the previously saved copy, run:
+\begin{Verbatim}
+  ./scripts/env revert
+\end{Verbatim}
+
+If you want, you can now create a second environment using the \texttt{new} command.
+It will ask you whether you want to make it a clone of the current environment (e.g.
+for minor changes) or if you want to start with a clean version (e.g. for selecting
+a new target).
+
+To switch to a different environment (e.g. \texttt{test1}), use:
+\begin{Verbatim}
+  ./scripts/env switch test1
+\end{Verbatim}
+
+To rename the current branch to a new name (e.g. \texttt{test2}), use:
+\begin{Verbatim}
+  ./scripts/env rename test2
+\end{Verbatim}
+
+If you want to get rid of environment switching and keep everything in the base directory
+again, use:
+\begin{Verbatim}
+  ./scripts/env clear
+\end{Verbatim}
-- 
cgit v1.2.3

