configure: remove --with-git= option

The scenario for which --with-git= was introduced was to use a SOCKS proxy
such as tsocks.  However, this was back in 2017 when QEMU's submodules
used the git:// protocol, and it is not as important when using the
"smart HTTP" backend; for example, neither "meson subprojects download"
nor scripts/checkpatch.pl obey the GIT environment variable.

So remove the knob, but test for the presence of git in the configure and
git-submodule.sh scripts, and suggest using --with-git-submodules=validate
+ a manual invocation of git-submodule.sh when git does not work.  Hopefully
in the future the GIT environment variable will be supported by Meson.

Reviewed-by: Thomas Huth <thuth@redhat.com>
Reviewed-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

scripts/ci/org.centos/stream/8/x86_64/configure

@@ -29,14 +29,12 @@
 --extra-cflags="-O2 -g -pipe -Wall -Werror=format-security -Wp,-D_FORTIFY_SOURCE=2 -Wp,-D_GLIBCXX_ASSERTIONS -fexceptions -fstack-protector-strong -grecord-gcc-switches -specs=/usr/lib/rpm/redhat/redhat-hardened-cc1 -specs=/usr/lib/rpm/redhat/redhat-annobin-cc1 -m64 -mtune=generic -fasynchronous-unwind-tables -fstack-clash-protection -fcf-protection" \
 --with-suffix="qemu-kvm" \
 --firmwarepath=/usr/share/qemu-firmware \
---with-git=meson \
 --with-git-submodules=update \
 --target-list="x86_64-softmmu" \
 --block-drv-rw-whitelist="qcow2,raw,file,host_device,nbd,iscsi,rbd,blkdebug,luks,null-co,nvme,copy-on-read,throttle,gluster" \
 --audio-drv-list="" \
 --block-drv-ro-whitelist="vmdk,vhdx,vpc,https,ssh" \
 --with-coroutine=ucontext \
---with-git=git \
 --tls-priority=@QEMU,SYSTEM \
 --disable-attr \
 --disable-auth-pam \

scripts/git-submodule.sh

@@ -12,7 +12,7 @@ maybe_modules="$@"
 # if --with-git-submodules=ignore, do nothing
 test "$command" = "ignore" && exit 0
 
-test -z "$GIT" && GIT=git
+test -z "$GIT" && GIT=$(command -v git)
 
 cd "$(dirname "$0")/.."
 
@@ -21,19 +21,14 @@ update_error() {
     echo
     echo "Unable to automatically checkout GIT submodules '$modules'."
     echo "If you require use of an alternative GIT binary (for example to"
-    echo "enable use of a transparent proxy), then please specify it by"
-    echo "running configure by with the '--with-git' argument. e.g."
-    echo
-    echo " $ ./configure --with-git='tsocks git'"
-    echo
-    echo "Alternatively you may disable automatic GIT submodule checkout"
-    echo "with:"
+    echo "enable use of a transparent proxy), please disable automatic"
+    echo "GIT submodule checkout with:"
     echo
     echo " $ ./configure --with-git-submodules=validate"
     echo
     echo "and then manually update submodules prior to running make, with:"
     echo
-    echo " $ scripts/git-submodule.sh update $modules"
+    echo " $ GIT='tsocks git' scripts/git-submodule.sh update $modules"
     echo
     exit 1
 }
@@ -57,6 +52,12 @@ then
     exit 1
 fi
 
+if test -n "$maybe_modules" && test -z "$GIT"
+then
+    echo "$0: unexpectedly called with submodules but git binary not found"
+    exit 1
+fi
+
 modules=""
 for m in $maybe_modules
 do