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-rw-r--r--doc/coding_style.mdwn2
-rw-r--r--doc/forum/Script_to_convert_config_files_for_inclusion_in_Propellor_config.mdwn41
-rw-r--r--doc/forum/Systemd.container_produces_non-standard_systemd_container/comment_4_5dc1c3ee7f111fcc36c72487b7713854._comment9
-rw-r--r--doc/news/version_2.14.0.mdwn14
-rw-r--r--doc/news/version_2.8.1.mdwn13
-rw-r--r--doc/todo/User.hasDesktopGroups:_debian-tor_group_doesn__39__t_necessarily_exist.mdwn10
-rw-r--r--doc/todo/pull_request:_Git.repoConfigured_and_Git.repoAcceptsNonFFs_properties.mdwn1
-rw-r--r--doc/todo/pull_request:_Locale.selectedFor_and_Locale.available_properties.mdwn15
-rw-r--r--doc/todo/pull_request:_Locale.selectedFor_and_Locale.available_properties/comment_1_3c528827f40420e3f4001f69127a0c51._comment17
-rw-r--r--doc/todo/pull_request:_Locale.selectedFor_and_Locale.available_properties/comment_2_981a305c50d699fd3d06c39ca66107ea._comment7
-rw-r--r--doc/todo/pull_request:_patch_Apt.buildDep_to_only_proceed_if_installable.mdwn3
-rw-r--r--doc/todo/pull_request:_patch_Apt.buildDep_to_only_proceed_if_installable/comment_10_eb58216ef1172ee5b882090dab7219ce._comment32
-rw-r--r--doc/todo/pull_request:_patch_Apt.buildDep_to_only_proceed_if_installable/comment_11_bee4b2397dfb28a3791081a83d725daf._comment7
-rw-r--r--doc/todo/pull_request:_patch_Apt.buildDep_to_only_proceed_if_installable/comment_1_88f5d79b8cd6064d1a65dec445819afe._comment14
-rw-r--r--doc/todo/pull_request:_patch_Apt.buildDep_to_only_proceed_if_installable/comment_2_23cb35130719bf1657652b76c0791947._comment10
-rw-r--r--doc/todo/pull_request:_patch_Apt.buildDep_to_only_proceed_if_installable/comment_3_5759b4fddf360e8a777c0339c5426b40._comment9
-rw-r--r--doc/todo/pull_request:_patch_Apt.buildDep_to_only_proceed_if_installable/comment_4_cd49645ff94d9ccec74ff72a836cd1f7._comment20
-rw-r--r--doc/todo/pull_request:_patch_Apt.buildDep_to_only_proceed_if_installable/comment_5_33744064a8b224d6e44e2cf8081f6a56._comment9
-rw-r--r--doc/todo/pull_request:_patch_Apt.buildDep_to_only_proceed_if_installable/comment_6_db48a08bc6eece590aebd41691623665._comment7
-rw-r--r--doc/todo/pull_request:_patch_Apt.buildDep_to_only_proceed_if_installable/comment_7_9c45f473cbc432a32bd64bbbf048fae4._comment21
-rw-r--r--doc/todo/pull_request:_patch_Apt.buildDep_to_only_proceed_if_installable/comment_8_7069f68888663fef109b82a044aeb5e1._comment9
-rw-r--r--doc/todo/pull_request:_patch_Apt.buildDep_to_only_proceed_if_installable/comment_9_5694c0bec217d3513aa8e80f55482d75._comment17
22 files changed, 274 insertions, 13 deletions
diff --git a/doc/coding_style.mdwn b/doc/coding_style.mdwn
index 219b367c..86a8516e 100644
--- a/doc/coding_style.mdwn
+++ b/doc/coding_style.mdwn
@@ -107,3 +107,5 @@ Note for emacs users: You can put the following snippet into a file called
(fill-column . 80)))
;; Warn about spaces used for indentation:
(haskell-mode . ((eval . (highlight-regexp "^ *")))))
+
+Also consider [haskell-tab-indent-mode](https://spwhitton.name/tech/code/haskell-tab-indent.el). The standard indentation modes that come with haskell-mode do not work well with tabs for indentation. This mode works well for hacking on Propellor. (A pull request has been submitted to have it included in haskell-mode.)
diff --git a/doc/forum/Script_to_convert_config_files_for_inclusion_in_Propellor_config.mdwn b/doc/forum/Script_to_convert_config_files_for_inclusion_in_Propellor_config.mdwn
new file mode 100644
index 00000000..c9f5ec8b
--- /dev/null
+++ b/doc/forum/Script_to_convert_config_files_for_inclusion_in_Propellor_config.mdwn
@@ -0,0 +1,41 @@
+This script turns
+
+ Section "Monitor"
+ Identifier "Configured Monitor"
+ EndSection
+
+into this:
+
+ [ "Section \"Monitor\""
+ , "\tIdentifier \"Configured Monitor\""
+ , "EndSection"
+ ]
+
+for the inclusion of short config files in your Propellor config using `File.hasContent`.
+
+[[!format haskell """
+#!/usr/bin/runhaskell
+
+main = interact $ unlines . propellorLines . lines
+
+propellorLines :: [String] -> [String]
+propellorLines (x:xs) = ("[ " ++ wrapEscapeLine x) : propellorLines' xs
+
+propellorLines' :: [String] -> [String]
+propellorLines' = foldr step ["]"]
+ where
+ step x xs = (", " ++ wrapEscapeLine x) : xs
+
+wrapEscapeLine :: String -> String
+wrapEscapeLine line = "\"" ++ (foldr step "" line) ++ "\""
+ where
+ step x xs
+ | x == '\t' = "\\t" ++ xs
+ | x == '\\' = x : x : xs
+ | x == '"' = '\\' : x : xs
+ | otherwise = x : xs
+"""]]
+
+Usage: `cat config_file | propellor_lines` (or in Emacs, dump the config file into your propellor config, select the region and use `C-u M-|` to pipe it through).
+
+-- [[spwhitton|https://spwhitton.name]]
diff --git a/doc/forum/Systemd.container_produces_non-standard_systemd_container/comment_4_5dc1c3ee7f111fcc36c72487b7713854._comment b/doc/forum/Systemd.container_produces_non-standard_systemd_container/comment_4_5dc1c3ee7f111fcc36c72487b7713854._comment
new file mode 100644
index 00000000..d7fe1dd5
--- /dev/null
+++ b/doc/forum/Systemd.container_produces_non-standard_systemd_container/comment_4_5dc1c3ee7f111fcc36c72487b7713854._comment
@@ -0,0 +1,9 @@
+[[!comment format=mdwn
+ username="jerryjacobs1989@d19093c366dfb2959c549ed1aff6175ddc7a7a5b"
+ nickname="jerryjacobs1989"
+ subject="Thank you"
+ date="2015-11-29T13:04:56Z"
+ content="""
+I was bitten also by this weird error message and have submitted it upstream:
+https://github.com/systemd/systemd/issues/2060
+"""]]
diff --git a/doc/news/version_2.14.0.mdwn b/doc/news/version_2.14.0.mdwn
new file mode 100644
index 00000000..2a6e7bda
--- /dev/null
+++ b/doc/news/version_2.14.0.mdwn
@@ -0,0 +1,14 @@
+propellor 2.14.0 released with [[!toggle text="these changes"]]
+[[!toggleable text="""
+ * Add Propellor.Property.PropellorRepo.hasOriginUrl, an explicit way to
+ set the git repository url normally implicitly set when using --spin.
+ * Added Chroot.noServices property.
+ * DiskImage creation automatically uses Chroot.noServices.
+ * Removed the (unused) dependency on quickcheck.
+ * DebianMirror: Added a DebianMirror type for configuration (API change)
+ Thanks, Félix Sipma.
+ * DebianMirror: Add RsyncExtra to configuration.
+ Thanks, Félix Sipma.
+ * Added Git.repoConfigured and Git.repoAcceptsNonFFs properties.
+ Thanks, Sean Whitton
+ * Added User.hasDesktopGroups property."""]] \ No newline at end of file
diff --git a/doc/news/version_2.8.1.mdwn b/doc/news/version_2.8.1.mdwn
deleted file mode 100644
index fafde5e4..00000000
--- a/doc/news/version_2.8.1.mdwn
+++ /dev/null
@@ -1,13 +0,0 @@
-propellor 2.8.1 released with [[!toggle text="these changes"]]
-[[!toggleable text="""
- * Guard against power loss etc when building propellor, by updating
- the executable atomically.
- * Added Logcheck module, contributed by Jelmer Vernooij.
- * Added Kerberos module, contributed by Jelmer Vernooij.
- * Privdata that uses HostContext inside a container will now have the
- name of the container as its context, rather than the name of
- the host(s) where the container is used. This allows eg, having different
- passwords for a user in different containers. Note that previously,
- propellor would prompt using the container name as the context, but
- not actually use privdata using that context; so this is a bug fix.
- * Fix --add-key to not fail committing when no privdata file exists yet."""]] \ No newline at end of file
diff --git a/doc/todo/User.hasDesktopGroups:_debian-tor_group_doesn__39__t_necessarily_exist.mdwn b/doc/todo/User.hasDesktopGroups:_debian-tor_group_doesn__39__t_necessarily_exist.mdwn
new file mode 100644
index 00000000..b6e1ec20
--- /dev/null
+++ b/doc/todo/User.hasDesktopGroups:_debian-tor_group_doesn__39__t_necessarily_exist.mdwn
@@ -0,0 +1,10 @@
+The new `User.hasDesktopGroups` tries to add a user to the group `debian-tor` which fails if this group does not exist.
+
+What package creates this group? If someone could let me know that, I will patch `User.hasDesktopGroups` to only try to add a user to `debian-tor` if `Apt.isInstalled "blah"` is true.
+
+Or perhaps Joey added this group because this group exists by default on Debian Unstable. If so then a check can be inserted for that.
+
+--[[spwhitton|https://spwhitton.name/]]
+
+> Noticed that too and made it only add the user to existant groups, which
+> is the same approach user-setup uses. [[done]] --[[Joey]]
diff --git a/doc/todo/pull_request:_Git.repoConfigured_and_Git.repoAcceptsNonFFs_properties.mdwn b/doc/todo/pull_request:_Git.repoConfigured_and_Git.repoAcceptsNonFFs_properties.mdwn
index 6bdd0b42..c1df5461 100644
--- a/doc/todo/pull_request:_Git.repoConfigured_and_Git.repoAcceptsNonFFs_properties.mdwn
+++ b/doc/todo/pull_request:_Git.repoConfigured_and_Git.repoAcceptsNonFFs_properties.mdwn
@@ -10,3 +10,4 @@ This branch adds
Note that `Git.repoConfigured` uses a tuple instead of just two function arguments in order that it can be used infix in `config.hs` when connected to other properties with `&`, as `ConfFile.containsIniSetting`.
> [[done]], thank you (had to fix some indents) --[[Joey]]
+>> Sorry about that! Thought I had Emacs set up for your style guide. --spwhitton
diff --git a/doc/todo/pull_request:_Locale.selectedFor_and_Locale.available_properties.mdwn b/doc/todo/pull_request:_Locale.selectedFor_and_Locale.available_properties.mdwn
new file mode 100644
index 00000000..b34118f0
--- /dev/null
+++ b/doc/todo/pull_request:_Locale.selectedFor_and_Locale.available_properties.mdwn
@@ -0,0 +1,15 @@
+Please consider merging branch `locale` of repo `https://git.spwhitton.name/propellor`
+
+It adds the following properties:
+
+- `Locale.selectedFor` to choose a locale for a locale variable
+- `Locale.available`, used by `Locale.selectedFor` to ensure a locale is generated
+
+Example usage (I'm British but I live in the US):
+
+ & "en_GB.UTF-8" `Locale.selectedFor` ["LANG", "LANGUAGE"]
+ & "en_US.UTF-8" `Locale.selectedFor` ["LC_PAPER"]
+
+Pretty sure I've got the indentation right this time too ;)
+
+> merged, thanks! [[done]] --[[Joey]]
diff --git a/doc/todo/pull_request:_Locale.selectedFor_and_Locale.available_properties/comment_1_3c528827f40420e3f4001f69127a0c51._comment b/doc/todo/pull_request:_Locale.selectedFor_and_Locale.available_properties/comment_1_3c528827f40420e3f4001f69127a0c51._comment
new file mode 100644
index 00000000..4d413c84
--- /dev/null
+++ b/doc/todo/pull_request:_Locale.selectedFor_and_Locale.available_properties/comment_1_3c528827f40420e3f4001f69127a0c51._comment
@@ -0,0 +1,17 @@
+[[!comment format=mdwn
+ username="joey"
+ subject="""comment 1"""
+ date="2015-11-25T15:24:10Z"
+ content="""
+The types here don't tell me much about what values it expects.
+
+`selectedFor :: String -> [String] -> Property NoInfo`
+
+Function needs either some examples in its haddock, or better types.
+
+Also, the `available` property incorrectly succeeds if the locale passed to
+it is not listed in locale.gen.
+
+(It would be nice for these properties to be revertable but that's just a
+thought.)
+"""]]
diff --git a/doc/todo/pull_request:_Locale.selectedFor_and_Locale.available_properties/comment_2_981a305c50d699fd3d06c39ca66107ea._comment b/doc/todo/pull_request:_Locale.selectedFor_and_Locale.available_properties/comment_2_981a305c50d699fd3d06c39ca66107ea._comment
new file mode 100644
index 00000000..e8801aba
--- /dev/null
+++ b/doc/todo/pull_request:_Locale.selectedFor_and_Locale.available_properties/comment_2_981a305c50d699fd3d06c39ca66107ea._comment
@@ -0,0 +1,7 @@
+[[!comment format=mdwn
+ username="spwhitton"
+ subject="comment 2"
+ date="2015-11-26T02:51:22Z"
+ content="""
+Thanks for the feedback. I've implemented your suggestions. Please take a look.
+"""]]
diff --git a/doc/todo/pull_request:_patch_Apt.buildDep_to_only_proceed_if_installable.mdwn b/doc/todo/pull_request:_patch_Apt.buildDep_to_only_proceed_if_installable.mdwn
new file mode 100644
index 00000000..a27dc2e1
--- /dev/null
+++ b/doc/todo/pull_request:_patch_Apt.buildDep_to_only_proceed_if_installable.mdwn
@@ -0,0 +1,3 @@
+Please consider merging branch `builddepfix` of repo `https://git.spwhitton.name/propellor`
+
+Patches `Apt.buildDep` to check whether the build deps are installable, so that it no longer registers a change every spin.
diff --git a/doc/todo/pull_request:_patch_Apt.buildDep_to_only_proceed_if_installable/comment_10_eb58216ef1172ee5b882090dab7219ce._comment b/doc/todo/pull_request:_patch_Apt.buildDep_to_only_proceed_if_installable/comment_10_eb58216ef1172ee5b882090dab7219ce._comment
new file mode 100644
index 00000000..3799a012
--- /dev/null
+++ b/doc/todo/pull_request:_patch_Apt.buildDep_to_only_proceed_if_installable/comment_10_eb58216ef1172ee5b882090dab7219ce._comment
@@ -0,0 +1,32 @@
+[[!comment format=mdwn
+ username="joey"
+ subject="""comment 10"""
+ date="2015-12-03T15:05:21Z"
+ content="""
+
+ trivial (trivial p `changesFile` f) `changesFile` f'
+
+The parenthesized property here is all marked trivial, so a change to f
+won't result in MadeChange, though a change to f' will.
+
+The only way propellor might intercept the output of a program is if you're
+using the new Concurrent module. In that case it should buffer program output
+and display it all at once. There could potentially be a bug there that
+hid program output. I certianly can't reproduce changesFile hiding the output
+of a program:
+
+ *Propellor.Property.Apt> runPropellor (Host "localhost" [] mempty) $ ensureProperty $ trivial (buildDep ["git-annex"]) `changesFile` "/var/lib/dpkg/status"
+ Reading package lists... Done
+ Building dependency tree
+ Reading state information... Done
+ 0 upgraded, 0 newly installed, 0 to remove and 707 not upgraded.
+ NoChange
+
+ *Propellor.Property.Apt Propellor.Property.Concurrent> withConcurrentOutput $ runPropellor (Host "localhost" [] mempty) $ ensureProperty $ (trivial (buildDep ["git-annex"]) `changesFile` "/var/lib/dpkg/status") `concurrently` cmdProperty "echo" ["hi"]
+ hi
+ Reading package lists...
+ Building dependency tree...
+ Reading state information...
+ 0 upgraded, 0 newly installed, 0 to remove and 707 not upgraded.
+ MadeChange
+"""]]
diff --git a/doc/todo/pull_request:_patch_Apt.buildDep_to_only_proceed_if_installable/comment_11_bee4b2397dfb28a3791081a83d725daf._comment b/doc/todo/pull_request:_patch_Apt.buildDep_to_only_proceed_if_installable/comment_11_bee4b2397dfb28a3791081a83d725daf._comment
new file mode 100644
index 00000000..f4df5527
--- /dev/null
+++ b/doc/todo/pull_request:_patch_Apt.buildDep_to_only_proceed_if_installable/comment_11_bee4b2397dfb28a3791081a83d725daf._comment
@@ -0,0 +1,7 @@
+[[!comment format=mdwn
+ username="spwhitton"
+ subject="comment 11"
+ date="2015-12-03T23:29:57Z"
+ content="""
+Thank you for your feedback. I'll think about how I might rewrite `changeIfChanges` to avoid that problem with `trivial`, and I'll try to pin down the hiding of apt's output.
+"""]]
diff --git a/doc/todo/pull_request:_patch_Apt.buildDep_to_only_proceed_if_installable/comment_1_88f5d79b8cd6064d1a65dec445819afe._comment b/doc/todo/pull_request:_patch_Apt.buildDep_to_only_proceed_if_installable/comment_1_88f5d79b8cd6064d1a65dec445819afe._comment
new file mode 100644
index 00000000..209b62a3
--- /dev/null
+++ b/doc/todo/pull_request:_patch_Apt.buildDep_to_only_proceed_if_installable/comment_1_88f5d79b8cd6064d1a65dec445819afe._comment
@@ -0,0 +1,14 @@
+[[!comment format=mdwn
+ username="joey"
+ subject="""comment 1"""
+ date="2015-11-26T11:14:37Z"
+ content="""
+Looks like Build-Depends-Index is not handled, nor are 'a | b' build deps,
+or arch-specific build deps. Since versions are skipped, if a build dep
+needed a newer version, the property also wouldn't try to upgrade to it
+after this change.
+
+I feel that parsing build deps is too complex for propellor.
+
+It might work to somehow detect if apt has made any changes.
+"""]]
diff --git a/doc/todo/pull_request:_patch_Apt.buildDep_to_only_proceed_if_installable/comment_2_23cb35130719bf1657652b76c0791947._comment b/doc/todo/pull_request:_patch_Apt.buildDep_to_only_proceed_if_installable/comment_2_23cb35130719bf1657652b76c0791947._comment
new file mode 100644
index 00000000..ace80098
--- /dev/null
+++ b/doc/todo/pull_request:_patch_Apt.buildDep_to_only_proceed_if_installable/comment_2_23cb35130719bf1657652b76c0791947._comment
@@ -0,0 +1,10 @@
+[[!comment format=mdwn
+ username="joey"
+ subject="""comment 2"""
+ date="2015-11-26T12:48:25Z"
+ content="""
+How about simply checking if /var/lib/dpkg/status is changed?
+
+I added a `changesFile` property combinator which should be helpful for
+that.
+"""]]
diff --git a/doc/todo/pull_request:_patch_Apt.buildDep_to_only_proceed_if_installable/comment_3_5759b4fddf360e8a777c0339c5426b40._comment b/doc/todo/pull_request:_patch_Apt.buildDep_to_only_proceed_if_installable/comment_3_5759b4fddf360e8a777c0339c5426b40._comment
new file mode 100644
index 00000000..86f4d1de
--- /dev/null
+++ b/doc/todo/pull_request:_patch_Apt.buildDep_to_only_proceed_if_installable/comment_3_5759b4fddf360e8a777c0339c5426b40._comment
@@ -0,0 +1,9 @@
+[[!comment format=mdwn
+ username="spwhitton"
+ subject="comment 3"
+ date="2015-11-26T14:39:31Z"
+ content="""
+I was hoping your deep knowledge of Apt would be able to help with this!
+
+Before I proceed, how would you feel about catching the output of apt and only printing it if apt did make changes? Although that would make the output weirdly appear all at once when the build deps are actually installed, on the other hand it would mean no output if they're not, when we detect no changes to /var/lib/dpkg/status.
+"""]]
diff --git a/doc/todo/pull_request:_patch_Apt.buildDep_to_only_proceed_if_installable/comment_4_cd49645ff94d9ccec74ff72a836cd1f7._comment b/doc/todo/pull_request:_patch_Apt.buildDep_to_only_proceed_if_installable/comment_4_cd49645ff94d9ccec74ff72a836cd1f7._comment
new file mode 100644
index 00000000..30149a4c
--- /dev/null
+++ b/doc/todo/pull_request:_patch_Apt.buildDep_to_only_proceed_if_installable/comment_4_cd49645ff94d9ccec74ff72a836cd1f7._comment
@@ -0,0 +1,20 @@
+[[!comment format=mdwn
+ username="joey"
+ subject="""comment 4"""
+ date="2015-11-30T16:57:45Z"
+ content="""
+I think it would probably depend on the user when that makes sense to do.
+If I'm installing build deps over a slow network connection, I'd like to
+see the output.
+
+It would be awesome if this transformation could be applied to any
+arbitrary Property. I don't immediately know how to do that, although it
+seems useful that all process spawning already goes through
+concurrent-output, which can buffer the output and display it only when the
+command finishes.
+
+Perhaps an extension to concurrent-ouput could let it buffer the output
+of all commands run by a property and then discard the buffer if the
+property finished with NoChange. But I don't see a way to make this work
+when multiple properties are being run concurrently.
+"""]]
diff --git a/doc/todo/pull_request:_patch_Apt.buildDep_to_only_proceed_if_installable/comment_5_33744064a8b224d6e44e2cf8081f6a56._comment b/doc/todo/pull_request:_patch_Apt.buildDep_to_only_proceed_if_installable/comment_5_33744064a8b224d6e44e2cf8081f6a56._comment
new file mode 100644
index 00000000..b0283161
--- /dev/null
+++ b/doc/todo/pull_request:_patch_Apt.buildDep_to_only_proceed_if_installable/comment_5_33744064a8b224d6e44e2cf8081f6a56._comment
@@ -0,0 +1,9 @@
+[[!comment format=mdwn
+ username="spwhitton"
+ subject="comment 5"
+ date="2015-12-02T04:46:14Z"
+ content="""
+I've made a property combinator `noChangeIfUnchanged` and applied it to Apt.buildDep in my `builddepfix` branch. Please take a look.
+
+In my testing of this, Propellor hides the output if the build deps are already installed i.e. if the property returns NoChange. So it looks like you've already implemented your awesome at some point :)
+"""]]
diff --git a/doc/todo/pull_request:_patch_Apt.buildDep_to_only_proceed_if_installable/comment_6_db48a08bc6eece590aebd41691623665._comment b/doc/todo/pull_request:_patch_Apt.buildDep_to_only_proceed_if_installable/comment_6_db48a08bc6eece590aebd41691623665._comment
new file mode 100644
index 00000000..85c91d65
--- /dev/null
+++ b/doc/todo/pull_request:_patch_Apt.buildDep_to_only_proceed_if_installable/comment_6_db48a08bc6eece590aebd41691623665._comment
@@ -0,0 +1,7 @@
+[[!comment format=mdwn
+ username="spwhitton"
+ subject="comment 6"
+ date="2015-12-02T04:57:57Z"
+ content="""
+Seems I blanked on your `changesFile` combinator when I sat down to write mine. Taking a look now, my approach is much more direct for cases like `Apt.buildDep` when the problem is registering a change when there should be NoChange, whereas I think the intention of your changesFile is the opposite case. Though it might be nice to combine them. Let me know what you think.
+"""]]
diff --git a/doc/todo/pull_request:_patch_Apt.buildDep_to_only_proceed_if_installable/comment_7_9c45f473cbc432a32bd64bbbf048fae4._comment b/doc/todo/pull_request:_patch_Apt.buildDep_to_only_proceed_if_installable/comment_7_9c45f473cbc432a32bd64bbbf048fae4._comment
new file mode 100644
index 00000000..e2611fd5
--- /dev/null
+++ b/doc/todo/pull_request:_patch_Apt.buildDep_to_only_proceed_if_installable/comment_7_9c45f473cbc432a32bd64bbbf048fae4._comment
@@ -0,0 +1,21 @@
+[[!comment format=mdwn
+ username="joey"
+ subject="""comment 7"""
+ date="2015-12-02T16:10:34Z"
+ content="""
+The two combinators are indeed very similar. The reason I wrote
+changesFile the way I did is that that allows it to be applied repeatedly
+when a property can change any of several files.
+
+ trivial someprop
+ `changesFile` "foo"
+ `changesFile` "bar"
+
+That seems fairly likely to come up, while it would be unusual for a
+property to have to change multiple files at once to be considered
+to make a change at all, which is what multiple applications of
+`noChangeIfUnchanged` leads to.
+
+But neither combinator causes apt's output to not be displayed,
+which is what I thought we were talking about.
+"""]]
diff --git a/doc/todo/pull_request:_patch_Apt.buildDep_to_only_proceed_if_installable/comment_8_7069f68888663fef109b82a044aeb5e1._comment b/doc/todo/pull_request:_patch_Apt.buildDep_to_only_proceed_if_installable/comment_8_7069f68888663fef109b82a044aeb5e1._comment
new file mode 100644
index 00000000..c05d6255
--- /dev/null
+++ b/doc/todo/pull_request:_patch_Apt.buildDep_to_only_proceed_if_installable/comment_8_7069f68888663fef109b82a044aeb5e1._comment
@@ -0,0 +1,9 @@
+[[!comment format=mdwn
+ username="spwhitton"
+ subject="comment 8"
+ date="2015-12-02T21:44:37Z"
+ content="""
+My original goal was to have `Apt.buildDep` return NoChange if the build deps are already installed. As a welcome but unexplained side-effect, on my system `noChangeIfUnchanged` *does* cause apt's output not to be displayed.
+
+I'll think about ways to combine our two combinators.
+"""]]
diff --git a/doc/todo/pull_request:_patch_Apt.buildDep_to_only_proceed_if_installable/comment_9_5694c0bec217d3513aa8e80f55482d75._comment b/doc/todo/pull_request:_patch_Apt.buildDep_to_only_proceed_if_installable/comment_9_5694c0bec217d3513aa8e80f55482d75._comment
new file mode 100644
index 00000000..5783dd7b
--- /dev/null
+++ b/doc/todo/pull_request:_patch_Apt.buildDep_to_only_proceed_if_installable/comment_9_5694c0bec217d3513aa8e80f55482d75._comment
@@ -0,0 +1,17 @@
+[[!comment format=mdwn
+ username="spwhitton"
+ subject="comment 9"
+ date="2015-12-03T02:08:58Z"
+ content="""
+I can get what I want if I use `trivial` and `changesFile` in the way you described. So please consider adding your method as a combinator:
+
+ p `changeIfChanges` f = (trivial p) `changesFile` f
+
+which is okay because `trivial` is idempotent so `changeIfChanges` may be applied more than once (I've got this in my branch with a decent docstring and I've applied it to `Apt.buildDep`).
+
+I think that this ought to be its own combinator, rather than just a recommendation to use `trivial` and `changesFile` in such cases, because this doesn't follow the semantics of `trivial`: it's not necessarily the case that it is the same amount of work to check if the property needs to be ensured as it is to ensure it.
+
+(In this language, my `noChangeIfUnchanged` could be called `changeOnlyIfChanges`. I agree that it's very unlikely to useful.)
+
+(Again, on my machine, applying `changeIfChanges` to `Apt.buildDep` magically hides apt's output if the build-deps are already installed.)
+"""]]