drop emacs-git stub for fedora >= 34 (#1882360)

Since git-2.18.0, the emacs files shipped in git have been stub files
which merely point users to better options.  Stop shipping these stubs
with Fedora 34 and later.

Drop the emacs BuildRequires on Fedora >= 34.  Elsewhere, replace it
with emacs-common.  We need macros.emacs for %{_emacs_sitelispdir}
anywhere we ship the stub .el files¹.

The full emacs BR _was_ necessary prior to git-2.18.0, as /usr/bin/emacs
was used to byte compile the .el files.  It traces all the way back to
e46bac5 (Add emacs-git package from Ville (#235431), 2007-06-22).

¹ It might be nice if there were an emacs-rpm-macros for this.  But
  emacs-common is a lot lighter than emacs, so it's still a nice
  improvement.  Per `dnf install` in a current f33 container image:

    $ dnf install emacs
    ...
    Install  193 Packages
    Total download size: 164 M
    Installed size: 544 M

    $ dnf install emacs-common
    ...
    Install  7 Packages
    Total download size: 36 M
    Installed size: 89 M

git.spec

@@ -6,6 +6,13 @@
 
 %global gitexecdir          %{_libexecdir}/git-core
 
+# Settings for Fedora >= 34
+%if 0%{?fedora} >= 34
+%bcond_with                 emacs
+%else
+%bcond_without              emacs
+%endif
+
 # Settings for Fedora
 %if 0%{?fedora}
 # linkchecker is not available on EL
@@ -141,7 +148,10 @@ BuildRequires:  linkchecker
 # endif with docs
 BuildRequires:  desktop-file-utils
 BuildRequires:  diffutils
-BuildRequires:  emacs
+%if %{with emacs}
+BuildRequires:  emacs-common
+%endif
+# endif emacs-common
 BuildRequires:  expat-devel
 BuildRequires:  findutils
 BuildRequires:  gawk
@@ -264,10 +274,16 @@ Requires:       perl(Term::ReadKey)
 # endif ! defined perl_bootstrap
 Requires:       perl-Git = %{version}-%{release}
 
-%if %{emacs_filesystem} && %{defined _emacs_version}
+%if %{with emacs} && %{emacs_filesystem} && %{defined _emacs_version}
 Requires:       emacs-filesystem >= %{_emacs_version}
 %endif
-# endif emacs_filesystem
+# endif with emacs && emacs_filesystem
+
+# Obsolete emacs-git if it's disabled
+%if %{without emacs}
+Obsoletes:      emacs-git < %{?epoch:%{epoch}:}%{version}-%{release}
+%endif
+# endif without emacs
 
 # Obsolete git-cvs if it's disabled
 %if %{without cvs}
@@ -317,10 +333,10 @@ Requires:       perl-Git = %{version}-%{release}
 Requires:       perl(Term::ReadKey)
 %endif
 # endif ! defined perl_bootstrap
-%if ! %{emacs_filesystem}
+%if %{with emacs} && ! %{emacs_filesystem}
 Requires:       emacs-git = %{version}-%{release}
 %endif
-# endif ! emacs_filesystem
+# endif with emacs && ! emacs_filesystem
 %description all
 Git is a fast, scalable, distributed revision control system with an
 unusually rich command set that provides both high-level operations
@@ -397,7 +413,7 @@ Requires:       perl(Net::SMTP::SSL)
 %description email
 %{summary}.
 
-%if ! %{emacs_filesystem}
+%if %{with emacs} && ! %{emacs_filesystem}
 %package -n emacs-git
 Summary:        Git version control system support for Emacs
 Requires:       git = %{version}-%{release}
@@ -408,7 +424,7 @@ Provides:       emacs-git-el = %{version}-%{release}
 %description -n emacs-git
 %{summary}.
 %endif
-# endif ! emacs_filesystem
+# endif with emacs && ! emacs_filesystem
 
 %package -n gitk
 Summary:        Git repository browser
@@ -644,6 +660,7 @@ sed -i -e '1s@#!\( */usr/bin/env python\|%{__python2}\)$@#!%{__python3}@' \
 
 %make_install -C contrib/contacts
 
+%if %{with emacs}
 %global elispdir %{_emacs_sitelispdir}/git
 pushd contrib/emacs >/dev/null
 for el in *.el ; do
@@ -653,6 +670,8 @@ for el in *.el ; do
     rm -f $el # clean up to avoid cruft in git-core-doc
 done
 popd >/dev/null
+%endif
+# endif with emacs
 
 %if %{with libsecret}
 install -pm 755 contrib/credential/libsecret/git-credential-libsecret \
@@ -910,10 +929,10 @@ rmdir --ignore-fail-on-non-empty "$testdir"
 # endif use_systemd
 
 %files -f bin-man-doc-git-files
-%if %{emacs_filesystem}
+%if %{with emacs} && %{emacs_filesystem}
 %{elispdir}
 %endif
-# endif emacs_filesystem
+# endif with emacs && emacs_filesystem
 %{_datadir}/git-core/contrib/diff-highlight
 %{_datadir}/git-core/contrib/hooks/multimail
 %{_datadir}/git-core/contrib/hooks/update-paranoid
@@ -980,12 +999,12 @@ rmdir --ignore-fail-on-non-empty "$testdir"
 %{?with_docs:%{_mandir}/man1/git-daemon*.1*}
 %{?with_docs:%{_pkgdocdir}/git-daemon*.html}
 
-%if ! %{emacs_filesystem}
+%if %{with emacs} && ! %{emacs_filesystem}
 %files -n emacs-git
 %{_pkgdocdir}/contrib/emacs/README
 %{elispdir}
 %endif
-# endif ! emacs_filesystem
+# endif with emacs && ! emacs_filesystem
 
 %files email
 %{_pkgdocdir}/*email*.txt
@@ -1059,6 +1078,7 @@ rmdir --ignore-fail-on-non-empty "$testdir"
 %changelog
 * Fri Oct 09 2020 Todd Zullinger <tmz@pobox.com> - 2.29.0-0.1.rc1
 - update to 2.29.0-rc1
+- drop emacs-git stub for fedora >= 34 (#1882360)
 
 * Mon Oct 05 2020 Todd Zullinger <tmz@pobox.com> - 2.29.0-0.0.rc0
 - update to 2.29.0-rc0