fix(make): show unique targets in subdirs

completions/make

@@ -46,7 +46,7 @@ _make_target_extract_script()
     /^$/ {                                      # end of target block
       x;                                        # unhold target
       /^$/d;                                    # dont print blanks
-      s|^${dirname_re-}\(.\{${#basename}\}[^:/]*/\{0,1\}\)[^:]*:.*$|${output}|p;
+      s|^${dirname_re-}\(.\{${#basename}\}[^:]*\):.*$|${output}|p;
       d;                                        # hide any bugs
     }
 
@@ -170,6 +170,53 @@ _make()
             ${makef+"${makef[@]}"} "${makef_dir[@]}" .DEFAULT 2>/dev/null |
             command sed -ne "$script"))
 
+        # discard the files under subdirectories unless the path is unique
+        # under each subdirectory and instead generate the subdirectory path.
+        # For example, when there are two candidates, "abc/def" and "abc/xyz",
+        # we generate "abc/" instead of generating both candidates directly.
+        # When there is only one candidate "abc/def", we generate the full path
+        # "abc/def".
+        local prefix=$cur
+        [[ $mode == -d ]] && prefix=
+        if ((${#COMPREPLY[@]} > 0)); then
+            # collect the possible completions including the directory names in
+            # `paths' and count the number of children of each subdirectory in
+            # `nchild'.
+            local -A paths nchild
+            local target
+            for target in "${COMPREPLY[@]}"; do
+                local path=${target%/}
+                while [[ ! ${paths[$path]+set} ]] &&
+                    paths[$path]=1 &&
+                    [[ $path == "$prefix"*/* ]]; do
+                    path=${path%/*}
+                    if [[ ! ${nchild[$path]+set} ]]; then
+                        ((nchild[\$path] = 1))
+                    else
+                        ((nchild[\$path]++))
+                    fi
+                done
+            done
+
+            COMPREPLY=()
+            local nreply=0
+            for target in "${!paths[@]}"; do
+                # generate only the paths that do not have a unique child and
+                # whose all parent and ancestor directories have a unique
+                # child.
+                ((${nchild[$target]-0} == 1)) && continue
+                local path=$target
+                while [[ $path == "$prefix"*/* ]]; do
+                    path=${path%/*}
+                    ((${nchild[$path]-0} == 1)) || continue 2
+                done
+
+                # suffix `/' when the target path is a subdiretory, which has
+                # at least one child.
+                COMPREPLY[nreply++]=$target${nchild[$target]+/}
+            done
+        fi
+
         if [[ $mode != -d ]]; then
             # Completion will occur if there is only one suggestion
             # so set options for completion based on the first one