Support compressing single files.

Modify imgutils.compress to allow the "rootdir" argument to be either a
directory or a single file to add to an archive.

(cherry picked from commit c585b91422)

src/pylorax/imgutils.py

@@ -36,8 +36,8 @@ from pylorax.executils import runcmd, runcmd_output
 
 ######## Functions for making container images (cpio, tar, squashfs) ##########
 
-def compress(command, rootdir, outfile, compression="xz", compressargs=None):
-    '''Make a compressed archive of the given rootdir.
+def compress(command, root, outfile, compression="xz", compressargs=None):
+    '''Make a compressed archive of the given rootdir or file.
     command is a list of the archiver commands to run
     compression should be "xz", "gzip", "lzma", "bzip2", or None.
     compressargs will be used on the compression commandline.'''
@@ -60,12 +60,23 @@ def compress(command, rootdir, outfile, compression="xz", compressargs=None):
         compression = "pbzip2"
         compressargs.insert(0, "-p%d" % multiprocessing.cpu_count())
 
-    logger.debug("find %s -print0 |%s | %s %s > %s", rootdir, " ".join(command),
-                 compression, " ".join(compressargs), outfile)
     find, archive, comp = None, None, None
+
     try:
-        find = Popen(["find", ".", "-print0"], stdout=PIPE, cwd=rootdir)
-        archive = Popen(command, stdin=find.stdout, stdout=PIPE, cwd=rootdir)
+        if os.path.isdir(root):
+            logger.debug("find %s -print0 |%s | %s %s > %s", root, " ".join(command),
+                    compression, " ".join(compressargs), outfile)
+
+            find = Popen(["find", ".", "-print0"], stdout=PIPE, cwd=root)
+            archive = Popen(command, stdin=find.stdout, stdout=PIPE, cwd=root)
+        else:
+            logger.debug("echo %s |%s | %s %s > %s", root, " ".join(command),
+                         compression, " ".join(compressargs), outfile)
+
+            archive = Popen(command, stdin=PIPE, stdout=PIPE, cwd=os.path.dirname(root))
+            archive.stdin.write(os.path.basename(root).encode("utf-8") + b"\0")
+            archive.stdin.close()
+
         comp = Popen([compression] + compressargs,
                      stdin=archive.stdout, stdout=open(outfile, "wb"))
         comp.wait()
@@ -76,18 +87,18 @@ def compress(command, rootdir, outfile, compression="xz", compressargs=None):
         list(p.kill() for p in (find, archive, comp) if p)
         return 1
 
-def mkcpio(rootdir, outfile, compression="xz", compressargs=None):
+def mkcpio(root, outfile, compression="xz", compressargs=None):
     compressargs = compressargs or ["-9"]
     return compress(["cpio", "--null", "--quiet", "-H", "newc", "-o"],
-                    rootdir, outfile, compression, compressargs)
+                    root, outfile, compression, compressargs)
 
-def mktar(rootdir, outfile, compression="xz", compressargs=None, selinux=True):
+def mktar(root, outfile, compression="xz", compressargs=None, selinux=True):
     compressargs = compressargs or ["-9"]
     tar_cmd = ["tar", "--no-recursion"]
     if selinux:
         tar_cmd += ["--selinux", "--acls", "--xattrs"]
     tar_cmd += ["-cf-", "--null", "-T-"]
-    return compress(tar_cmd, rootdir, outfile, compression, compressargs)
+    return compress(tar_cmd, root, outfile, compression, compressargs)
 
 def mksquashfs(rootdir, outfile, compression="default", compressargs=None):
     '''Make a squashfs image containing the given rootdir.'''

tests/pylorax/test_imgutils.py

@@ -17,6 +17,7 @@
 import glob
 import os
 import parted
+import tarfile
 import tempfile
 import unittest
 
@@ -154,6 +155,17 @@ class ImgUtilsTest(unittest.TestCase):
                     file_details = get_file_magic(disk_img.name)
                     self.assertTrue(magic in file_details, (compression, magic, file_details))
 
+    def mktar_single_file_test(self):
+        with tempfile.NamedTemporaryFile(prefix="lorax.test.disk.") as disk_img,\
+                tempfile.NamedTemporaryFile(prefix="lorax.test.input.") as input_file:
+            mktar(input_file.name, disk_img.name, compression=None)
+
+            self.assertTrue(os.path.exists(disk_img.name))
+            self.assertTrue(tarfile.is_tarfile(disk_img.name))
+
+            with tarfile.TarFile(disk_img.name) as t:
+                self.assertEqual(t.getnames(), [os.path.basename(input_file.name)])
+
     def mksquashfs_test(self):
         """Test mksquashfs function"""
         with tempfile.TemporaryDirectory(prefix="lorax.test.") as work_dir: