Match output of Compat Top API to Docker

We were only splitting on tabs, not spaces, so we returned just a
single line most of the time, not an array of the fields in the
output of `ps`. Unfortunately, some of these fields are allowed
to contain spaces themselves, which makes things complicated, but
we got lucky in that Docker took the simplest possible solution
and just assumed that only one field would contain spaces and it
would always be the last one, which is easy enough to duplicate
on our end.

Fixes #23981

Signed-off-by: Matt Heon <mheon@redhat.com>

pkg/api/handlers/compat/containers_top.go

@@ -88,12 +88,23 @@ loop: // break out of for/select infinite` loop
 				}
 
 				for _, line := range output[1:] {
-					process := strings.Split(line, "\t")
-					for i := range process {
-						process[i] = strings.TrimSpace(process[i])
-					}
+					process := strings.FieldsFunc(line, func(r rune) bool {
+						return r == ' ' || r == '\t'
+					})
+					if len(process) > len(body.Titles) {
+						// Docker assumes the last entry is *always* command
+						// Which can include spaces.
+						// All other descriptors are assumed to NOT include extra spaces.
+						// So combine any extras.
+						cmd := strings.Join(process[len(body.Titles)-1:], " ")
+						var finalProc []string
+						finalProc = append(finalProc, process[:len(body.Titles)-1]...)
+						finalProc = append(finalProc, cmd)
+						body.Processes = append(body.Processes, finalProc)
+					} else {
 						body.Processes = append(body.Processes, process)
 					}
+				}
 
 				if err := encoder.Encode(body); err != nil {
 					if !statusWritten {

test/apiv2/20-containers.at

@@ -144,6 +144,14 @@ if root; then
     podman rm -f $CTRNAME
 fi
 
+# Verify that compat top endpoint combines multi-entry COMMAND lines
+CTRNAME=testtopproc
+podman run --name $CTRNAME -d $IMAGE sleep 25
+t GET containers/$CTRNAME/top?stream=false 200 \
+  .Processes.[0].[6]="00:00:00" \
+  .Processes.[0].[7]="sleep 25"
+podman rm -f -t0 $CTRNAME
+
 CTRNAME=test123
 podman run --name $CTRNAME -d $IMAGE top
 t GET libpod/containers/$CTRNAME/top?ps_args=--invalid 500 \