diff --git a/tools/atree/atree.cpp b/tools/atree/atree.cpp
new file mode 100644
index 0000000..aee2b3c
--- /dev/null
+++ b/tools/atree/atree.cpp
@@ -0,0 +1,301 @@
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+#include "options.h"
+#include "files.h"
+#include "fs.h"
+#include <set>
+#include <iostream>
+#include <sstream>
+
+using namespace std;
+
+bool g_debug = false;
+vector<string> g_listFiles;
+vector<string> g_inputBases;
+map<string, string> g_variables;
+string g_outputBase;
+string g_dependency;
+bool g_useHardLinks = false;
+
+const char* USAGE =
+"\n"
+"Usage: atree OPTIONS\n"
+"\n"
+"Options:\n"
+"  -f FILELIST    Specify one or more files containing the\n"
+"                 list of files to copy.\n"
+"  -I INPUTDIR    Specify one or more base directories in\n"
+"                 which to look for the files\n"
+"  -o OUTPUTDIR   Specify the directory to copy all of the\n"
+"                 output files to.\n"
+"  -l             Use hard links instead of copying the files.\n"
+"  -m DEPENDENCY  Output a make-formatted file containing the list.\n"
+"                 of files included.  It sets the variable ATREE_FILES.\n"
+"  -v VAR=VAL     Replaces ${VAR} by VAL when reading input files.\n"
+"\n"
+"FILELIST file format:\n"
+"  The FILELIST files contain the list of files that will end up\n"
+"  in the final OUTPUTDIR.  Atree will look for files in the INPUTDIR\n"
+"  directories in the order they are specified.\n"
+"\n"
+"  In a FILELIST file, comment lines start with a #.  Other lines\n"
+"  are of the format:\n"
+"\n"
+"    DEST\n"
+"    SRC DEST\n"
+"    -SRCPATTERN\n"
+"\n"
+"  DEST should be path relative to the output directory.\n"
+"  If SRC is supplied, the file names can be different.\n"
+"  SRCPATTERN is a pattern for the filenames.\n"
+"\n";
+
+int usage()
+{
+    fwrite(USAGE, strlen(USAGE), 1, stderr);
+    return 1;
+}
+
+static bool
+add_variable(const char* arg) {
+    const char* p = arg;
+    while (*p && *p != '=') p++;
+
+    if (*p == 0 || p == arg || p[1] == 0) {
+        return false;
+    }
+
+    ostringstream var;
+    var << "${" << string(arg, p-arg) << "}";
+    g_variables[var.str()] = string(p+1);
+    return true;
+}
+
+int
+main(int argc, char* const* argv)
+{
+    int err;
+    bool done = false;
+    while (!done) {
+        int opt = getopt(argc, argv, "f:I:o:hlm:v:");
+        switch (opt)
+        {
+            case -1:
+                done = true;
+                break;
+            case 'f':
+                g_listFiles.push_back(string(optarg));
+                break;
+            case 'I':
+                g_inputBases.push_back(string(optarg));
+                break;
+            case 'o':
+                if (g_outputBase.length() != 0) {
+                    fprintf(stderr, "%s: -o may only be supplied once -- "
+                                "-o %s\n", argv[0], optarg);
+                    return usage();
+                }
+                g_outputBase = optarg;
+                break;
+            case 'l':
+                g_useHardLinks = true;
+                break;
+            case 'm':
+                if (g_dependency.length() != 0) {
+                    fprintf(stderr, "%s: -m may only be supplied once -- "
+                                "-m %s\n", argv[0], optarg);
+                    return usage();
+                }
+                g_dependency = optarg;
+                break;
+            case 'v':
+                if (!add_variable(optarg)) {
+                    fprintf(stderr, "%s Invalid expression in '-v %s': "
+                            "expected format is '-v VAR=VALUE'.\n",
+                            argv[0], optarg);
+                    return usage();
+                }
+                break;
+            default:
+            case '?':
+            case 'h':
+                return usage();
+        }
+    }
+    if (optind != argc) {
+        fprintf(stderr, "%s: invalid argument -- %s\n", argv[0], argv[optind]);
+        return usage();
+    }
+
+    if (g_listFiles.size() == 0) {
+        fprintf(stderr, "%s: At least one -f option must be supplied.\n",
+                 argv[0]);
+        return usage();
+    }
+
+    if (g_inputBases.size() == 0) {
+        fprintf(stderr, "%s: At least one -I option must be supplied.\n",
+                 argv[0]);
+        return usage();
+    }
+
+    if (g_outputBase.length() == 0) {
+        fprintf(stderr, "%s: -o option must be supplied.\n", argv[0]);
+        return usage();
+    }
+
+
+#if 0
+    for (vector<string>::iterator it=g_listFiles.begin();
+                                it!=g_listFiles.end(); it++) {
+        printf("-f \"%s\"\n", it->c_str());
+    }
+    for (vector<string>::iterator it=g_inputBases.begin();
+                                it!=g_inputBases.end(); it++) {
+        printf("-I \"%s\"\n", it->c_str());
+    }
+    printf("-o \"%s\"\n", g_outputBase.c_str());
+    if (g_useHardLinks) {
+        printf("-l\n");
+    }
+#endif
+
+    vector<FileRecord> files;
+    vector<FileRecord> more;
+    vector<string> excludes;
+    set<string> directories;
+    set<string> deleted;
+
+    // read file lists
+    for (vector<string>::iterator it=g_listFiles.begin();
+                                it!=g_listFiles.end(); it++) {
+        err = read_list_file(*it, g_variables, &files, &excludes);
+        if (err != 0) {
+            return err;
+        }
+    }
+
+    // look for input files
+    err = 0;
+    for (vector<FileRecord>::iterator it=files.begin();
+                                it!=files.end(); it++) {
+        err |= locate(&(*it), g_inputBases);
+
+    }
+    
+    // expand the directories that we should copy into a list of files
+    for (vector<FileRecord>::iterator it=files.begin();
+                                it!=files.end(); it++) {
+        if (it->sourceIsDir) {
+            err |= list_dir(*it, excludes, &more);
+        }
+    }
+    for (vector<FileRecord>::iterator it=more.begin();
+                                it!=more.end(); it++) {
+        files.push_back(*it);
+    }
+
+    // get the name and modtime of the output files
+    for (vector<FileRecord>::iterator it=files.begin();
+                                it!=files.end(); it++) {
+        stat_out(g_outputBase, &(*it));
+    }
+
+    if (err != 0) {
+        return 1;
+    }
+
+    // gather directories
+    for (vector<FileRecord>::iterator it=files.begin();
+                                it!=files.end(); it++) {
+        if (it->sourceIsDir) {
+            directories.insert(it->outPath);
+        } else {
+            string s = dir_part(it->outPath);
+            if (s != ".") {
+                directories.insert(s);
+            }
+        }
+    }
+
+    // gather files that should become directores and directories that should
+    // become files
+    for (vector<FileRecord>::iterator it=files.begin();
+                                it!=files.end(); it++) {
+        if (it->outMod != 0 && it->sourceIsDir != it->outIsDir) {
+            deleted.insert(it->outPath);
+        }
+    }
+
+    // delete files
+    for (set<string>::iterator it=deleted.begin();
+                                it!=deleted.end(); it++) {
+        if (g_debug) {
+            printf("deleting %s\n", it->c_str());
+        }
+        err = remove_recursively(*it);
+        if (err != 0) {
+            return err;
+        }
+    }
+
+    // make directories
+    for (set<string>::iterator it=directories.begin();
+                                it!=directories.end(); it++) {
+        if (g_debug) {
+            printf("mkdir %s\n", it->c_str());
+        }
+        err = mkdir_recursively(*it);
+        if (err != 0) {
+            return err;
+        }
+    }
+
+    // copy (or link) files
+    for (vector<FileRecord>::iterator it=files.begin();
+                                it!=files.end(); it++) {
+        if (!it->sourceIsDir) {
+            if (g_debug) {
+                printf("copy %s(%ld) ==> %s(%ld)", it->sourcePath.c_str(),
+                    it->sourceMod, it->outPath.c_str(), it->outMod);
+                fflush(stdout);
+            }
+
+            if (it->outMod < it->sourceMod) {
+                err = copy_file(it->sourcePath, it->outPath);
+                if (g_debug) {
+                    printf(" done.\n");
+                }
+                if (err != 0) {
+                    return err;
+                }
+            } else {
+                if (g_debug) {
+                    printf(" skipping.\n");
+                }
+            }
+        }
+    }
+
+    // output the dependency file
+    if (g_dependency.length() != 0) {
+        FILE *f = fopen(g_dependency.c_str(), "w");
+        if (f != NULL) {
+            fprintf(f, "ATREE_FILES := $(ATREE_FILES) \\\n");
+            for (vector<FileRecord>::iterator it=files.begin();
+                                it!=files.end(); it++) {
+                if (!it->sourceIsDir) {
+                    fprintf(f, "%s \\\n", it->sourcePath.c_str());
+                }
+            }
+            fprintf(f, "\n");
+            fclose(f);
+        } else {
+            fprintf(stderr, "error opening manifest file for write: %s\n",
+                    g_dependency.c_str());
+        }
+    }
+
+    return 0;
+}