packaging: allow running packaging with custom uid+gid for CentOS

rpmbuild in CentOS 7 has a bug causing rpmbuild to fail
with "Bad owner/group" if spec or source files are owned
by a different user: https://github.com/rpm-software-management/rpm/issues/2

This makes it very annoying to try and build the CentOS RPMs
on CentOS with Docker.

As an alternative, this change makes it possible to do so,
using an environment variable.

Differential Revision: https://phab.mercurial-scm.org/D5571

contrib/packaging/docker/centos5

@@ -1,7 +1,7 b''
 FROM centos:centos5
 
-RUN groupadd -g 1000 build && \
-    useradd -u 1000 -g 1000 -s /bin/bash -d /build -m build
+RUN groupadd -g %GID% build && \
+    useradd -u %UID% -g %GID% -s /bin/bash -d /build -m build
 
 RUN \
 	sed -i 's/^mirrorlist/#mirrorlist/' /etc/yum.repos.d/*.repo && \

contrib/packaging/docker/centos6

@@ -1,7 +1,7 b''
 FROM centos:centos6
 
-RUN groupadd -g 1000 build && \
-    useradd -u 1000 -g 1000 -s /bin/bash -d /build -m build
+RUN groupadd -g %GID% build && \
+    useradd -u %UID% -g %GID% -s /bin/bash -d /build -m build
 
 RUN yum install -y \
 	gcc \

contrib/packaging/docker/centos7

@@ -1,7 +1,7 b''
 FROM centos:centos7
 
-RUN groupadd -g 1000 build && \
-    useradd -u 1000 -g 1000 -s /bin/bash -d /build -m build
+RUN groupadd -g %GID% build && \
+    useradd -u %UID% -g %GID% -s /bin/bash -d /build -m build
 
 RUN yum install -y \
 	gcc \

contrib/packaging/dockerrpm

@@ -10,7 +10,15 b' DOCKER=$($BUILDDIR/hg-docker docker-path'
 
 CONTAINER=hg-docker-$PLATFORM
 
-$BUILDDIR/hg-docker build $BUILDDIR/docker/$PLATFORM $CONTAINER
+if [[ -z "${HG_DOCKER_OWN_USER}" ]]; then
+    DOCKERUID=1000
+    DOCKERGID=1000
+else
+    DOCKERUID=$(id -u)
+    DOCKERGID=$(id -g)
+fi
+
+$BUILDDIR/hg-docker build --build-arg UID=$DOCKERUID --build-arg GID=$DOCKERGID $BUILDDIR/docker/$PLATFORM $CONTAINER
 
 RPMBUILDDIR=$ROOTDIR/packages/$PLATFORM
 $ROOTDIR/contrib/packaging/buildrpm --rpmbuilddir $RPMBUILDDIR --prepare $*

contrib/packaging/hg-docker

@@ -47,7 +47,7 b' def get_dockerfile(path: pathlib.Path, a'
         df = fh.read()
 
     for k, v in args:
-        df = df.replace(b'%%%s%%' % k, v)
+        df = df.replace(bytes('%%%s%%' % k.decode(), 'utf-8'), v)
 
     return df