Git installation

Normally you can just do "make" followed by "make install", and that
will install the git programs in your own ~/bin/ directory.  If you want
to do a global install, you can do

        $ make prefix=/usr all doc info ;# as yourself
        # make prefix=/usr install install-doc install-html install-info ;# as root

(or prefix=/usr/local, of course).  Just like any program suite
that uses $prefix, the built results have some paths encoded,
which are derived from $prefix, so "make all; make prefix=/usr
install" would not work.

The beginning of the Makefile documents many variables that affect the way
git is built.  You can override them either from the command line, or in a
config.mak file.

Alternatively you can use autoconf generated ./configure script to
set up install paths (via config.mak.autogen), so you can write instead

        $ make configure ;# as yourself
        $ ./configure --prefix=/usr ;# as yourself
        $ make all doc ;# as yourself
        # make install install-doc install-html;# as root

If you're willing to trade off (much) longer build time for a later
faster git you can also do a profile feedback build with

        $ make prefix=/usr profile
        # make prefix=/usr PROFILE=BUILD install

This will run the complete test suite as training workload and then
rebuild git with the generated profile feedback. This results in a git
which is a few percent faster on CPU intensive workloads.  This
may be a good tradeoff for distribution packagers.

Alternatively you can run profile feedback only with the git benchmark
suite. This runs significantly faster than the full test suite, but
has less coverage:

        $ make prefix=/usr profile-fast
        # make prefix=/usr PROFILE=BUILD install

Or if you just want to install a profile-optimized version of git into
your home directory, you could run:

        $ make profile-install

or
        $ make profile-fast-install

As a caveat: a profile-optimized build takes a *lot* longer since the
git tree must be built twice, and in order for the profiling
measurements to work properly, ccache must be disabled and the test
suite has to be run using only a single CPU.  In addition, the profile
feedback build stage currently generates a lot of additional compiler
warnings.

Issues of note:

 - Ancient versions of GNU Interactive Tools (pre-4.9.2) installed a
   program "git", whose name conflicts with this program.  But with
   version 4.9.2, after long hiatus without active maintenance (since
   around 1997), it changed its name to gnuit and the name conflict is no
   longer a problem.

   NOTE: When compiled with backward compatibility option, the GNU
   Interactive Tools package still can install "git", but you can build it
   with --disable-transition option to avoid this.

 - You can use git after building but without installing if you want
   to test drive it.  Simply run git found in bin-wrappers directory
   in the build directory, or prepend that directory to your $PATH.
   This however is less efficient than running an installed git, as
   you always need an extra fork+exec to run any git subcommand.

   It is still possible to use git without installing by setting a few
   environment variables, which was the way this was done
   traditionally.  But using git found in bin-wrappers directory in
   the build directory is far simpler.  As a historical reference, the
   old way went like this:

        GIT_EXEC_PATH=`pwd`
        PATH=`pwd`:$PATH
        GITPERLLIB=`pwd`/perl/build/lib
        export GIT_EXEC_PATH PATH GITPERLLIB

 - By default (unless NO_PERL is provided) Git will ship various perl
   scripts. However, for simplicity it doesn't use the
   ExtUtils::MakeMaker toolchain to decide where to place the perl
   libraries. Depending on the system this can result in the perl
   libraries not being where you'd like them if they're expected to be
   used by things other than Git itself.

   Manually supplying a perllibdir prefix should fix this, if this is
   a problem you care about, e.g.:

       prefix=/usr perllibdir=/usr/$(/usr/bin/perl -MConfig -wle 'print substr $Config{installsitelib}, 1 + length $Config{siteprefixexp}')

   Will result in e.g. perllibdir=/usr/share/perl/5.26.1 on Debian,
   perllibdir=/usr/share/perl5 (which we'd use by default) on CentOS.

 - Unless NO_PERL is provided Git will ship various perl libraries it
   needs. Distributors of Git will usually want to set
   NO_PERL_CPAN_FALLBACKS if NO_PERL is not provided to use their own
   copies of the CPAN modules Git needs.

 - Git is reasonably self-sufficient, but does depend on a few external
   programs and libraries.  Git can be used without most of them by adding
   the approriate "NO_<LIBRARY>=YesPlease" to the make command line or
   config.mak file.

        - "zlib", the compression library. Git won't build without it.

        - "ssh" is used to push and pull over the net.

        - A POSIX-compliant shell is required to run many scripts needed
          for everyday use (e.g. "bisect", "pull").

        - "Perl" version 5.8 or later is needed to use some of the
          features (e.g. preparing a partial commit using "git add -i/-p",
          interacting with svn repositories with "git svn").  If you can
          live without these, use NO_PERL.  Note that recent releases of
          Redhat/Fedora are reported to ship Perl binary package with some
          core modules stripped away (see http://lwn.net/Articles/477234/),
          so you might need to install additional packages other than Perl
          itself, e.g. Time::HiRes.

        - git-imap-send needs the OpenSSL library to talk IMAP over SSL if
          you are using libcurl older than 7.34.0.  Otherwise you can use
          NO_OPENSSL without losing git-imap-send.

          By default, git uses OpenSSL for SHA1 but it will use its own
          library (inspired by Mozilla's) with either NO_OPENSSL or
          BLK_SHA1.  Also included is a version optimized for PowerPC
          (PPC_SHA1).

        - "libcurl" library is used by git-http-fetch, git-fetch, and, if
          the curl version >= 7.34.0, for git-imap-send.  You might also
          want the "curl" executable for debugging purposes. If you do not
          use http:// or https:// repositories, and do not want to put
          patches into an IMAP mailbox, you do not have to have them
          (use NO_CURL).

        - "expat" library; git-http-push uses it for remote lock
          management over DAV.  Similar to "curl" above, this is optional
          (with NO_EXPAT).

        - "wish", the Tcl/Tk windowing shell is used in gitk to show the
          history graphically, and in git-gui.  If you don't want gitk or
          git-gui, you can use NO_TCLTK.

        - A gettext library is used by default for localizing Git. The
          primary target is GNU libintl, but the Solaris gettext
          implementation also works.

          We need a gettext.h on the system for C code, gettext.sh (or
          Solaris gettext(1)) for shell scripts, and libintl-perl for Perl
          programs.

          Set NO_GETTEXT to disable localization support and make Git only
          use English. Under autoconf the configure script will do this
          automatically if it can't find libintl on the system.

        - Python version 2.4 or later (but not 3.x, which is not
          supported by Perforce) is needed to use the git-p4 interface
          to Perforce.

 - Some platform specific issues are dealt with Makefile rules,
   but depending on your specific installation, you may not
   have all the libraries/tools needed, or you may have
   necessary libraries at unusual locations.  Please look at the
   top of the Makefile to see what can be adjusted for your needs.
   You can place local settings in config.mak and the Makefile
   will include them.  Note that config.mak is not distributed;
   the name is reserved for local settings.

 - To build and install documentation suite, you need to have
   the asciidoc/xmlto toolchain.  Because not many people are
   inclined to install the tools, the default build target
   ("make all") does _not_ build them.

   "make doc" builds documentation in man and html formats; there are
   also "make man", "make html" and "make info". Note that "make html"
   requires asciidoc, but not xmlto. "make man" (and thus make doc)
   requires both.

   "make install-doc" installs documentation in man format only; there
   are also "make install-man", "make install-html" and "make
   install-info".

   Building and installing the info file additionally requires
   makeinfo and docbook2X.  Version 0.8.3 is known to work.

   Building and installing the pdf file additionally requires
   dblatex.  Version >= 0.2.7 is known to work.

   All formats require at least asciidoc 8.4.1.

   There are also "make quick-install-doc", "make quick-install-man"
   and "make quick-install-html" which install preformatted man pages
   and html documentation. To use these build targets, you need to
   clone two separate git-htmldocs and git-manpages repositories next
   to the clone of git itself.

   It has been reported that docbook-xsl version 1.72 and 1.73 are
   buggy; 1.72 misformats manual pages for callouts, and 1.73 needs
   the patch in contrib/patches/docbook-xsl-manpages-charmap.patch

   Users attempting to build the documentation on Cygwin may need to ensure
   that the /etc/xml/catalog file looks something like this:

   <?xml version="1.0"?>
   <!DOCTYPE catalog PUBLIC
      "-//OASIS//DTD Entity Resolution XML Catalog V1.0//EN"
      "http://www.oasis-open.org/committees/entity/release/1.0/catalog.dtd"
   >
   <catalog xmlns="urn:oasis:names:tc:entity:xmlns:xml:catalog">
     <rewriteURI
       uriStartString = "http://docbook.sourceforge.net/release/xsl/current"
       rewritePrefix = "/usr/share/sgml/docbook/xsl-stylesheets"
     />
     <rewriteURI
       uriStartString="http://www.oasis-open.org/docbook/xml/4.5"
       rewritePrefix="/usr/share/sgml/docbook/xml-dtd-4.5"
     />
  </catalog>

  This can be achieved with the following two xmlcatalog commands:

  xmlcatalog --noout \
     --add rewriteURI \
        http://docbook.sourceforge.net/release/xsl/current \
        /usr/share/sgml/docbook/xsl-stylesheets \
     /etc/xml/catalog

  xmlcatalog --noout \
     --add rewriteURI \
         http://www.oasis-open.org/docbook/xml/4.5/xsl/current \
         /usr/share/sgml/docbook/xml-dtd-4.5 \
     /etc/xml/catalog