[netcf-devel] [PATCH] build - apply patchfiles to rpm build dir using git

[Laine Stump]

Rather than requiring a matching "patchXXX -p1" line in the specfile
for each "PatchXXX: blah.patch", this patch modifies the specfile so
that all that is needed is a list of patches ala "Patch XXX:
blah.patch", and uses git in a cleverly written (by Jirka Denemark
<jdenemar(a)redhat.com&gt; for the libvirt specfile) script to apply any
patches found in the spec. Here is Jirka's comment from the commit log
in libvirt:

    With this change, any patch declared in libvirt.spec with Patch[0-9]* is
    automatically applied in %prep. Unlike with the standard %patch[0-9]*,
    patches are applied with "git am" to avoid some unexpected results.
    However, as a result of this, all patches must be in the right format
    for "git am" to be able to apply them; they should ideally be generated
    from git using "git format-patch".

It also has the advantage that when you "prep" a new source directory,
it is setup with a git tree so that you can easily create new patches
to add to the rpm (by "git commit"ing the changes, then "git
format-patch ..." to create the patchfiles).
---
 netcf.spec.in | 51 +++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 51 insertions(+)

diff --git a/netcf.spec.in b/netcf.spec.in
index ed17402..1b64ff1 100644
--- a/netcf.spec.in
+++ b/netcf.spec.in
@@ -9,11 +9,26 @@ URL:            https://fedorahosted.org/netcf/
 Source0:        https://fedorahosted.org/released/%{name}/%{name}-%{version}.tar.gz
 BuildRoot:      %{_tmppath}/%{name}-%{version}-%{release}-root-%(%{__id_u} -n)
 
+# Patches
+# One patch per line, in this format:
+# Patch001: file1.patch
+# Patch002: file2.patch
+# ...
+#
+# The patches will automatically be put into the build source tree
+# during the %prep stage (using git, which is now required for an rpm
+# build)
+#
+
 # Default to skipping autoreconf.  Distros can change just this one
 # line (or provide a command-line override) if they backport any
 # patches that touch configure.ac or Makefile.am.
 %{!?enable_autotools:%define enable_autotools 0}
 
+# git is used to build a source tree with patches applied (see the
+# %prep section)
+BuildRequires: git
+
 # Fedora 20 / RHEL-7 are where netcf first uses systemd. Although earlier
 # Fedora has systemd, netcf still used sysvinit there.
 %if 0%{?fedora} >= 20 || 0%{?rhel} >= 7
@@ -88,6 +103,42 @@ The libraries for %{name}.
 %prep
 %setup -q
 
+# Patches have to be stored in a temporary file because RPM has
+# a limit on the length of the result of any macro expansion;
+# if the string is longer, it's silently cropped
+%{lua:
+    tmp = os.tmpname();
+    f = io.open(tmp, "w+");
+    count = 0;
+    for i, p in ipairs(patches) do
+        f:write(p.."\n");
+        count = count + 1;
+    end;
+    f:close();
+    print("PATCHCOUNT="..count.."\n")
+    print("PATCHLIST="..tmp.."\n")
+}
+
+git init -q
+git config user.name rpm-build
+git config user.email rpm-build
+git config gc.auto 0
+git add .
+git commit -q -a --author 'rpm-build <rpm-build>' \
+           -m '%{name}-%{version} base'
+
+COUNT=$(grep '\.patch$' $PATCHLIST | wc -l)
+if [ $COUNT -ne $PATCHCOUNT ]; then
+    echo "Found $COUNT patches in $PATCHLIST, expected $PATCHCOUNT"
+    exit 1
+fi
+if [ $COUNT -gt 0 ]; then
+    xargs git am <$PATCHLIST || exit 1
+fi
+echo "Applied $COUNT patches"
+rm -f $PATCHLIST
+
+
 %build
 %if %{with_libnl1}
 %define _with_libnl1 --with-libnl1
-- 
1.9.3