You can skip all of the following by downloading a pre-compiled binary appropriate for your platform and putting that self-contained binary someplace on your $PATH. To uninstall, simply delete the binary. To upgrade from an older release, just overwrite the older binary with the newer one.
Building and installing is very simple. Three steps:
Fossil is self-hosting, so you can obtain a ZIP archive containing a snapshot of the latest version directly from fossil's own fossil repository. Follow these steps:
Point your web browser at http://www.fossil-scm.org/. Click on the "Login" menu button.
Log in as anonymous. The password is shown on screen. The reason for requiring this login is to prevent spiders from walking the entire website, downloading ZIP archives of every historical version, and thereby soaking up all our bandwidth.
Click on the Timeline link at the top of the page.
Select a version of of fossil you want to download. Click on its link. Note that you must successfully log in as "anonymous" in step 1 above in order to see the link to the detailed version information.
Finally, click on one of the "Zip Archive" or "Tarball" links, according to your preference. These link will build a ZIP archive or a gzip-compressed tarball of the complete source code and download it to your browser.
Unpack the ZIP or tarball you downloaded into that directory then cd into the directory created.
If you do not have the OpenSSL library installed on your system, then add --with-openssl=none to omit the https functionality.
To build a statically linked binary (suitable for use inside a chroot jail) add the --static option.
Other configuration options can be seen by running ./configure --help
Run make to build the "fossil" or "fossil.exe" executable. The details depend on your platform and compiler.
Unix → the configure-generated Makefile should work on all unix and unix-like systems. Simply type "make".
Unix without running "configure" → if you prefer to avoid running configure, you can also use: make -f Makefile.classic. You may want to make minor edits to Makefile.classic to configure the build for your system.
Msys/MinGW → Use the mingw makefile: "make -f win/Makefile.mingw"
VC++ → Use the msc makefile. First change to the "win/" subdirectory ("cd win") then run "nmake /f Makefile.msc".
Note that Fossil requires the "zlib" compression library. This library is available by default on most unix systems, but it will typically have to be installed separately on windows systems. For windows builds, you may need to edit the makefile to tell it exactly where zlib is located on your system.
The finished binary is named "fossil" (or "fossil.exe" on windows). Put this binary in a directory that is somewhere on your PATH environment variable. It does not matter where.
(Optional:) To uninstall, just delete the binary.