Merge ~mwhudson/curtin:msftres into curtin:master

[Michael Hudson-Doyle]

support "msftres" as a (GPT-only) partition flag

We want to mark the recovery / reset partition as a "Microsoft Reserved
Partition" as GUI disk utilities hide such partitions, so add support
for this as a value for a partition flag. I chose "msftres" because
that's what parted calls this (although it maps msftres to type code
0x27 for a DOS partition table, which I think is wrong so I'm not doing
that).

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[Dan Bungert (dbungert)]

Thanks!

review: Approve

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diff --git a/curtin/commands/block_meta.py b/curtin/commands/block_meta.py
index 314d2c7..34acd75 100644
--- a/curtin/commands/block_meta.py
+++ b/curtin/commands/block_meta.py
@@ -52,6 +52,7 @@ SGDISK_FLAGS = {
     "home": '8302',
     "linux": '8300',
     "lvm": '8e00',
+    "msftres": '0c01',
     "prep": '4100',
     "raid": 'fd00',
     "swap": '8200',
@@ -921,8 +922,8 @@ def verify_size(devpath, expected_size_bytes, part_info):
 
 
 def verify_ptable_flag(devpath, expected_flag, label, part_info):
-    if (expected_flag not in SGDISK_FLAGS.keys()) and (expected_flag not in
-                                                       MSDOS_FLAGS.keys()):
+    if expected_flag not in SGDISK_FLAGS and \
+       expected_flag not in MSDOS_FLAGS:
         raise RuntimeError(
             'Cannot verify unknown partition flag: %s' % expected_flag)
 
diff --git a/curtin/storage_config.py b/curtin/storage_config.py
index 1e9b696..329183a 100644
--- a/curtin/storage_config.py
+++ b/curtin/storage_config.py
@@ -24,6 +24,7 @@ GPT_GUID_TO_CURTIN_MAP = {
     '9E1A2D38-C612-4316-AA26-8B49521E5A8B': 'prep',
     'A19D880F-05FC-4D3B-A006-743F0F84911E': 'raid',
     '0657FD6D-A4AB-43C4-84E5-0933C84B4F4F': 'swap',
+    'E3C9E316-0B5C-4DB8-817D-F92DF00215AE': 'msftres',
 }
 
 # MBR types
diff --git a/doc/topics/storage.rst b/doc/topics/storage.rst
index ba1ff73..918f3cd 100644
--- a/doc/topics/storage.rst
+++ b/doc/topics/storage.rst
@@ -423,7 +423,7 @@ disks.
   prior to creating the partition to ensure that other block layers or devices
   do not enable themselves and prevent accessing the partition.
 
-**flag**: *logical, extended, boot, bios_grub, swap, lvm, raid, home, prep*
+**flag**: *logical, extended, boot, bios_grub, swap, lvm, raid, home, prep, msftres*
 
 If the ``flag`` key is present, curtin will set the specified flag on the
 partition. Note that some flags only apply to msdos partition tables, and some
@@ -434,9 +434,9 @@ on a msdos table. An extended partition should be created containing all of the
 empty space on the drive, and logical partitions can be created within it. A
 extended partition must already be present to create logical partitions.
 
-On msdos partition tables, the *boot* flag sets the boot parameter to that
-partition. On gpt partition tables, the boot flag sets the esp flag on the
-partition.
+On msdos partition tables, the *boot* flag sets the boot parameter to
+that partition. On gpt partition tables, the boot flag sets partition
+type guid to the appropriate value for the EFI System Partition / ESP.
 
 If the host system for curtin has been booted using UEFI then curtin will
 install grub to the esp partition. If the system installation media
@@ -450,7 +450,7 @@ filesystem or be mounted anywhere on the system.
 **partition_type**: *msdos: byte value in 0xnn style; gpt: GUID*
 
 Only applicable to v2 storage configuration.  If both ``partition_type`` and
-``flag`` are set, ``partition_type`` dictates the acutal type.
+``flag`` are set, ``partition_type`` dictates the actual type.
 
 The ``partition_type`` field allows for setting arbitrary partition type values
 that do not have a matching ``flag``, or cases that are not handled by the
diff --git a/tests/integration/test_block_meta.py b/tests/integration/test_block_meta.py
index a2368e8..acd12e1 100644
--- a/tests/integration/test_block_meta.py
+++ b/tests/integration/test_block_meta.py
@@ -1283,3 +1283,16 @@ table-length: 256'''.encode()
         self.assertPartitions(
             PartData(number=1, offset=1 << 20, size=1 << 20, boot=False,
                      partition_type='82'))
+
+    @parameterized.expand(((1,), (2,)))
+    def test_msftres(self, sv):
+        self.img = self.tmp_path('image.img')
+        config = StorageConfigBuilder(version=sv)
+        config.add_image(path=self.img, create=True, size='20M',
+                         ptable='gpt')
+        config.add_part(number=1, offset=1 << 20, size=1 << 20, flag='msftres')
+        self.run_bm(config.render())
+
+        self.assertPartitions(
+            PartData(number=1, offset=1 << 20, size=1 << 20, boot=False,
+                     partition_type='E3C9E316-0B5C-4DB8-817D-F92DF00215AE'))