Fix saltstack/salt#1896

* Added `source` support to `salt.states.file.append()`
 * Added tests for the above.

salt/states/file.py

@@ -1710,7 +1710,7 @@ def uncomment(name, regex, char='#', backup='.bak'):
     return ret
 
 
-def append(name, text, makedirs=False):
+def append(name, text=None, makedirs=False, source=None, source_hash=None):
     '''
     Ensure that some text appears at the end of a file
 
@@ -1755,6 +1755,24 @@ def append(name, text, makedirs=False):
     if not check_res:
         return _error(ret, check_msg)
 
+    if source:
+        # get cached file or copy it to cache
+        cached_source_path = __salt__['cp.cache_file'](source)
+        logger.debug(
+            "state file.append cached source {0} -> {1}".format(
+                source, cached_source_path
+            )
+        )
+        cached_source = managed(
+            cached_source_path, source=source, source_hash=source_hash
+        )
+        if cached_source['result'] is True:
+            logger.debug(
+                "state file.append is loading text contents from cached source "
+                "{0}({1})".format(source, cached_source_path)
+            )
+            text = open(cached_source_path, 'r').read()
+
     if isinstance(text, string_types):
         text = (text,)
 

tests/integration/files/file/base/testappend/firstif

@@ -0,0 +1,4 @@
+# set variable identifying the chroot you work in (used in the prompt below)
+if [ -z "$debian_chroot" ] && [ -r /etc/debian_chroot ]; then
+    debian_chroot=$(cat /etc/debian_chroot)
+fi

tests/integration/files/file/base/testappend/init.sls

@@ -0,0 +1,3 @@
+/tmp/salttest/test.append:
+  file:
+    - touch

tests/integration/files/file/base/testappend/secondif

@@ -0,0 +1,4 @@
+# enable bash completion in interactive shells
+if [ -f /etc/bash_completion ] && ! shopt -oq posix; then
+    . /etc/bash_completion
+fi

tests/integration/files/file/base/testappend/step-1.sls

@@ -0,0 +1,4 @@
+/tmp/salttest/test.append:
+
+  file.append:
+    - source: salt://testappend/firstif

tests/integration/files/file/base/testappend/step-2.sls

@@ -0,0 +1,3 @@
+/tmp/salttest/test.append:
+  file.append:
+    - source: salt://testappend/secondif

tests/integration/modules/state.py

@@ -7,6 +7,9 @@ class StateModuleTest(integration.ModuleCase):
     '''
     Validate the test module
     '''
+
+    maxDiff = None
+
     def test_show_highstate(self):
         '''
         state.show_highstate
@@ -45,6 +48,40 @@ class StateModuleTest(integration.ModuleCase):
         sls = self.run_function('state.show_sls', mods='recurse_ok_two')
         self.assertIn('/etc/nagios/nrpe.cfg', sls)
 
+    def test_issue_1896_file_append_source(self):
+        '''
+        Verify that we can append a file's contents
+        '''
+        self.run_function('state.sls', mods='testappend')
+        self.run_function('state.sls', mods='testappend.step-1')
+        self.run_function('state.sls', mods='testappend.step-2')
+        self.assertMultiLineEqual("""\
+# set variable identifying the chroot you work in (used in the prompt below)
+if [ -z "$debian_chroot" ] && [ -r /etc/debian_chroot ]; then
+    debian_chroot=$(cat /etc/debian_chroot)
+fi
+# enable bash completion in interactive shells
+if [ -f /etc/bash_completion ] && ! shopt -oq posix; then
+    . /etc/bash_completion
+fi
+
+""", open("/tmp/salttest/test.append", "r").read())
+
+        # Re-append switching order
+        self.run_function('state.sls', mods='testappend.step-2')
+        self.run_function('state.sls', mods='testappend.step-1')
+        self.assertMultiLineEqual("""\
+# set variable identifying the chroot you work in (used in the prompt below)
+if [ -z "$debian_chroot" ] && [ -r /etc/debian_chroot ]; then
+    debian_chroot=$(cat /etc/debian_chroot)
+fi
+# enable bash completion in interactive shells
+if [ -f /etc/bash_completion ] && ! shopt -oq posix; then
+    . /etc/bash_completion
+fi
+
+""", open("/tmp/salttest/test.append", "r").read())
+
     def test_issue_1876_syntax_error(self):
         '''
         verify that we catch the following syntax error::
@@ -65,8 +102,6 @@ class StateModuleTest(integration.ModuleCase):
             'multiple state decs of the same type', sls
         )
 
-    maxDiff = None
-
     def test_issue_1879_too_simple_contains_check(self):
         contents = """\
 # set variable identifying the chroot you work in (used in the prompt below)