installation: put $SYSCONFDIR (/etc) under $PREFIX by default

Installation.md

@@ -1,17 +1,23 @@
-## Debian
+# Installing git-extras
+
+## Installing with a package manager
+
+### Debian
 
 ```bash
 $ sudo $apt_pref update
 $ sudo $apt_pref install git-extras
 ```
 
-## Mac
+### Mac OS X with Homebrew
 
 ```bash
 $ brew install git-extras
 ```
 
-## Clone / Tarball:
+## Building from source
+
+Obtain the git-extras source by cloning [its GitHub repo](https://github.com/tj/git-extras.git) or downloading a tarball of a [release](https://github.com/tj/git-extras/releases). Then install it by doing `make install` from the source tree.
 
 ```bash
 $ git clone https://github.com/tj/git-extras.git
@@ -21,12 +27,41 @@ $ git checkout $(git describe --tags $(git rev-list --tags --max-count=1))
 $ [sudo] make install
 ```
 
+By default, git-extras is installed under `/usr/local`. To install it at an
+alternate location, specify a `PREFIX` when calling `make`.
+
+```bash
+# Non-root users can install under their home directory
+make install PREFIX=$HOME/software
+
+# For third-party software kept under /opt
+make install PREFIX=/opt
+```
+
+If you want to relocate the bulk of the installation but still have configuration
+files installed to the system `/etc` dir or other alternate location, you can
+specify `SYSCONFDIR` in addition to `PREFIX`.
+
+```
+$ sudo make install PREFIX=/usr/local SYSCONFDIR=/etc
+```
+
+See the Makefile for details on advanced configuration options.
+
+## Installing from network
+
 One-liner:
 
 ```bash
 curl -sSL http://git.io/git-extras-setup | sudo bash /dev/stdin
 ```
 
+## Updating
+
+If you installed git-extras with a package manager, use that package manager's tools to update it.
+
+If you installed git-extras from source, you can run `git-extras update` to update it to the latest release. Be aware that this may lose any configuration options you specified during the original installation.
+
 ## Windows (use it at your own risk)
 
 First, please install `Git for Windows 2.x` from 'https://github.com/git-for-windows/git/releases'
@@ -48,6 +83,7 @@ install.cmd "C:\SCM\PortableGit\mingw64"
 
 Last, please copy `colrm.exe` and `column.exe` from `folder-your-msys2-installed/usr/bin` to
 `folder-your-git-installed/usr/bin`.
+
 Enjoy `git-extras`!
 
-[1]: http://sourceforge.net/projects/msys2/
+[1]: http://sourceforge.net/projects/msys2/

Makefile

@@ -1,7 +1,7 @@
 PREFIX ?= /usr/local
 BINPREFIX ?= "$(PREFIX)/bin"
 MANPREFIX ?= "$(PREFIX)/share/man/man1"
-SYSCONFDIR ?= /etc
+SYSCONFDIR ?= $(PREFIX)/etc
 BINS = $(wildcard bin/git-*)
 MANS = $(wildcard man/git-*.md)
 MAN_HTML = $(MANS:.md=.html)