Hashes in lockfile are diff friendly

This reworks the version and hash printing in the lockfile to minimize
diff changes:

- the version is on its own line so that the locks are mostly the same
  aside from the last line
- the hashes are each printed on one line with the package name for
  simpler diffing too.

rebar.lock

@@ -1,32 +1,24 @@
-{"1.1.0",[{<<"bbmustache">>,{pkg,<<"bbmustache">>,<<"1.0.4">>},0},
-          {<<"certifi">>,{pkg,<<"certifi">>,<<"0.4.0">>},0},
-          {<<"cf">>,{pkg,<<"cf">>,<<"0.2.1">>},0},
-          {<<"cth_readable">>,{pkg,<<"cth_readable">>,<<"1.2.2">>},0},
-          {<<"erlware_commons">>,{pkg,<<"erlware_commons">>,<<"0.21.0">>},0},
-          {<<"eunit_formatters">>,{pkg,<<"eunit_formatters">>,<<"0.3.1">>},0},
-          {<<"getopt">>,{pkg,<<"getopt">>,<<"0.8.2">>},0},
-          {<<"providers">>,{pkg,<<"providers">>,<<"1.6.0">>},0},
-          {<<"relx">>,{pkg,<<"relx">>,<<"3.19.0">>},0},
-          {<<"ssl_verify_hostname">>,
-           {pkg,<<"ssl_verify_hostname">>,<<"1.0.5">>},
-           0}]}.
-[{pkg_hash,[{<<"bbmustache">>,
-             <<"7BA94F971C5AFD7B6617918A4BB74705E36CAB36EB84B19B6A1B7EE06427AA38">>},
-            {<<"certifi">>,
-             <<"A7966EFB868B179023618D29A407548F70C52466BF1849B9E8EBD0E34B7EA11F">>},
-            {<<"cf">>,
-             <<"69D0B1349FD4D7D4DC55B7F407D29D7A840BF9A1EF5AF529F1EBE0CE153FC2AB">>},
-            {<<"cth_readable">>,
-             <<"983913A8E8572310B7EAF5F2631148B7D70B3C090D2120DCFE777A93AA4165FB">>},
-            {<<"erlware_commons">>,
-             <<"A04433071AD7D112EDEFC75AC77719DD3E6753E697AC09428FC83D7564B80B15">>},
-            {<<"eunit_formatters">>,
-             <<"7A6FC351EB5B873E2356B8852EB751E20C13A72FBCA03393CF682B8483509573">>},
-            {<<"getopt">>,
-             <<"B17556DB683000BA50370B16C0619DF1337E7AF7ECBF7D64FBF8D1D6BCE3109B">>},
-            {<<"providers">>,
-             <<"DB0E2F9043AE60C0155205FCD238D68516331D0E5146155E33D1E79DC452964A">>},
-            {<<"relx">>,
-             <<"286DD5244B4786F56AAC75D5C8E2D1FB4CFD306810D4EC8548F3AE1B3AADB8F7">>},
-            {<<"ssl_verify_hostname">>,
-             <<"2E73E068CD6393526F9FA6D399353D7C9477D6886BA005F323B592D389FB47BE">>}]}].
+{"1.1.0",
+[{<<"bbmustache">>,{pkg,<<"bbmustache">>,<<"1.0.4">>},0},
+ {<<"certifi">>,{pkg,<<"certifi">>,<<"0.4.0">>},0},
+ {<<"cf">>,{pkg,<<"cf">>,<<"0.2.1">>},0},
+ {<<"cth_readable">>,{pkg,<<"cth_readable">>,<<"1.2.2">>},0},
+ {<<"erlware_commons">>,{pkg,<<"erlware_commons">>,<<"0.21.0">>},0},
+ {<<"eunit_formatters">>,{pkg,<<"eunit_formatters">>,<<"0.3.1">>},0},
+ {<<"getopt">>,{pkg,<<"getopt">>,<<"0.8.2">>},0},
+ {<<"providers">>,{pkg,<<"providers">>,<<"1.6.0">>},0},
+ {<<"relx">>,{pkg,<<"relx">>,<<"3.19.0">>},0},
+ {<<"ssl_verify_hostname">>,{pkg,<<"ssl_verify_hostname">>,<<"1.0.5">>},0}]}.
+[
+{pkg_hash,[
+ {<<"bbmustache">>, <<"7BA94F971C5AFD7B6617918A4BB74705E36CAB36EB84B19B6A1B7EE06427AA38">>},
+ {<<"certifi">>, <<"A7966EFB868B179023618D29A407548F70C52466BF1849B9E8EBD0E34B7EA11F">>},
+ {<<"cf">>, <<"69D0B1349FD4D7D4DC55B7F407D29D7A840BF9A1EF5AF529F1EBE0CE153FC2AB">>},
+ {<<"cth_readable">>, <<"983913A8E8572310B7EAF5F2631148B7D70B3C090D2120DCFE777A93AA4165FB">>},
+ {<<"erlware_commons">>, <<"A04433071AD7D112EDEFC75AC77719DD3E6753E697AC09428FC83D7564B80B15">>},
+ {<<"eunit_formatters">>, <<"7A6FC351EB5B873E2356B8852EB751E20C13A72FBCA03393CF682B8483509573">>},
+ {<<"getopt">>, <<"B17556DB683000BA50370B16C0619DF1337E7AF7ECBF7D64FBF8D1D6BCE3109B">>},
+ {<<"providers">>, <<"DB0E2F9043AE60C0155205FCD238D68516331D0E5146155E33D1E79DC452964A">>},
+ {<<"relx">>, <<"286DD5244B4786F56AAC75D5C8E2D1FB4CFD306810D4EC8548F3AE1B3AADB8F7">>},
+ {<<"ssl_verify_hostname">>, <<"2E73E068CD6393526F9FA6D399353D7C9477D6886BA005F323B592D389FB47BE">>}]}
+].

src/rebar_config.erl

@@ -82,10 +82,29 @@ write_lock_file(LockFile, Locks) ->
             file:write_file(LockFile, io_lib:format("~p.~n", [NewLocks]));
         _ ->
             file:write_file(LockFile,
-                            io_lib:format("{~p,~p}.~n~p.~n",
-                                          [?CONFIG_VERSION, NewLocks, Attrs]))
+                            io_lib:format("{~p,~n~p}.~n[~n~s~n].~n",
+                                          [?CONFIG_VERSION, NewLocks,
+                                           format_attrs(Attrs)]))
     end.
 
+%% Attributes have a special formatting to ensure there's only one per
+%% line in terms of pkg_hash, so we disturb source diffing as little
+%% as possible.
+format_attrs([]) -> [];
+format_attrs([{pkg_hash, Vals}|T]) ->
+    [io_lib:format("{pkg_hash,[~n",[]), format_hashes(Vals), "]}",
+     maybe_comma(T) | format_attrs(T)];
+format_attrs([H|T]) ->
+    [io_lib:format("~p~s", [H, maybe_comma(T)]) | format_attrs(T)].
+
+format_hashes([]) -> [];
+format_hashes([{Pkg,Hash}|T]) ->
+    [" {", io_lib:format("~p",[Pkg]), ", ", io_lib:format("~p", [Hash]), "}",
+     maybe_comma(T) | format_hashes(T)].
+
+maybe_comma([]) -> "";
+maybe_comma([_|_]) -> io_lib:format(",~n", []).
+
 read_attrs(_Vsn, Locks, Attrs) ->
     %% Beta copy does not know how to expand attributes, but
     %% is ready to support it.