Besides being unused, this function has a bug that it will incorrectly
decode the path component Ubuntu\04016.04.2\040LTS\040amd64 as
"Ubuntu.04.2 LTS amd64" instead of "Ubuntu 16.04.2 LTS amd64".
This adds an argument "rev" specififying the Git commit hash. The
existing argument "rev" is renamed to "ref". The default value for
"ref" is "master". When specifying a hash, it's necessary to specify a
ref since we're not cloning the entire repository but only fetching a
specific ref.
Example usage:
builtins.fetchgit {
url = https://github.com/NixOS/nixpkgs.git;
ref = "release-16.03";
rev = "c1c0484041ab6f9c6858c8ade80a8477c9ae4442";
};
The package list is now cached in
~/.cache/nix/package-search.json. This gives a substantial speedup to
"nix search" queries. For example (on an SSD):
First run: (no package search cache, cold page cache)
$ time nix search blender
Attribute name: nixpkgs.blender
Package name: blender
Version: 2.78c
Description: 3D Creation/Animation/Publishing System
real 0m6.516s
Second run: (package search cache populated)
$ time nix search blender
Attribute name: nixpkgs.blender
Package name: blender
Version: 2.78c
Description: 3D Creation/Animation/Publishing System
real 0m0.143s
In particular, don't use base-64, which we don't support. (We do have
base-32 redirects for hysterical reasons.)
Also, add a test for the hashed mirror feature.
This doesn't work in read-only mode, ensuring that operations like
nix path-info --store https://cache.nixos.org -S nixpkgs.hello
(asking for the closure size of nixpkgs.hello in cache.nixos.org) work
when nixpkgs.hello doesn't exist in the local store.
On second though this was annoying. E.g. "nix log nixpkgs.hello" would
build/download Hello first, even though the log can be fetched
directly from the binary cache.
May need to revisit this.
This allows builds to call setuid binaries. This was previously
possible until we started using seccomp. Turns out that seccomp by
default disallows processes from acquiring new privileges. Generally,
any use of setuid binaries (except those created by the builder
itself) is by definition impure, but some people were relying on this
ability for certain tests.
Example:
$ nix build '(with import <nixpkgs> {}; runCommand "foo" {} "/run/wrappers/bin/ping -c 1 8.8.8.8; exit 1")' --no-allow-new-privileges
builder for ‘/nix/store/j0nd8kv85hd6r4kxgnwzvr0k65ykf6fv-foo.drv’ failed with exit code 1; last 2 log lines:
cannot raise the capability into the Ambient set
: Operation not permitted
$ nix build '(with import <nixpkgs> {}; runCommand "foo" {} "/run/wrappers/bin/ping -c 1 8.8.8.8; exit 1")' --allow-new-privileges
builder for ‘/nix/store/j0nd8kv85hd6r4kxgnwzvr0k65ykf6fv-foo.drv’ failed with exit code 1; last 6 log lines:
PING 8.8.8.8 (8.8.8.8) 56(84) bytes of data.
64 bytes from 8.8.8.8: icmp_seq=1 ttl=46 time=15.2 ms
Fixes#1429.
Functions like copyClosure() had 3 bool arguments, which creates a
severe risk of mixing up arguments.
Also, implement copyClosure() using copyPaths().
Cygwin sqlite3 is patched to call SetDllDirectory("/usr/bin") on init, which
affects the current process and is inherited by child processes. It causes
DLLs to be loaded from /usr/bin/ before $PATH, which breaks all sorts of
things. A typical failures would be header/lib version mismatches (e.g.
openssl when running checkPhase on openssh). We'll just set it back to the
default value.
Note that this is a problem with the cygwin version of sqlite3 (currently
3.18.0). nixpkgs doesn't have the problematic patch.
There's no reason to restrict this to Error exceptions. This shouldn't
matter to #1407 since the repl doesn't catch non-Error exceptions
anyway, but you never know...
Recently aws-sdk-cpp quietly switched to using S3 virtual host URIs
(https://github.com/aws/aws-sdk-cpp/commit/69d9c53882), i.e. it sends
requests to http://<bucket>.<region>.s3.amazonaws.com rather than
http://<region>.s3.amazonaws.com/<bucket>. However this interacts
badly with curl connection reuse. For example, if we do the following:
1) Check whether a bucket exists using GetBucketLocation.
2) If it doesn't, create it using CreateBucket.
3) Do operations on the bucket.
then 3) will fail for a minute or so with a NoSuchBucket exception,
presumably because the server being hit is a fallback for cases when
buckets don't exist.
Disabling the use of virtual hosts ensures that 3) succeeds
immediately. (I don't know what S3's consistency guarantees are for
bucket creation, but in practice buckets appear to be available
immediately.)
Newer versions of aws-sdk-cpp call CalculateDelayBeforeNextRetry()
even for non-retriable errors (like NoSuchKey) whih causes log spam in
hydra-queue-runner.
Sandboxes cannot be nested, so if Nix's build runs inside a sandbox,
it cannot use a sandbox itself. I don't see a clean way to detect
whether we're in a sandbox, so use a test-specific hack.
https://github.com/NixOS/nix/issues/1413
In particular, UF_IMMUTABLE (uchg) needs to be cleared to allow the
path to be garbage-collected or optimised.
See https://github.com/NixOS/nixpkgs/issues/25819.
+ the file from being garbage-collected.
Thus, instead of ‘--option <name> <value>’, you can write ‘--<name>
<value>’. So
--option http-connections 100
becomes
--http-connections 100
Apart from brevity, the difference is that it's not an error to set a
non-existent option via --option, but unrecognized arguments are
fatal.
Boolean options have special treatment: they're mapped to the
argument-less flags ‘--<name>’ and ‘--no-<name>’. E.g.
--option auto-optimise-store false
becomes
--no-auto-optimise-store
Even with "build-use-sandbox = false", we now use sandboxing with a
permissive profile that allows everything except the creation of
setuid/setgid binaries.
Also, add rules to allow fixed-output derivations to access the
network.
These rules are sufficient to build stdenvDarwin without any
__sandboxProfile magic.
The filename used was not unique and owned by the build user, so
builds could fail with
error: while setting up the build environment: cannot unlink ‘/nix/store/99i210ihnsjacajaw8r33fmgjvzpg6nr-bison-3.0.4.drv.sb’: Permission denied
runResolver() was barfing on directories like
/System/Library/Frameworks/Security.framework/Versions/Current/PlugIns. It
should probably do something sophisticated for frameworks, but let's
ignore them for now.
This fixes
error: getting attributes of path ‘Versions/Current/CoreFoundation’: No such file or directory
when /System/Library/Frameworks/CoreFoundation.framework/CoreFoundation is a symlink.
Also fixes a segfault when encounting a file that is not a MACH binary (such
as /dev/null, which is included in __impureHostDeps in Nixpkgs).
Possibly fixes#786.
Fixes
src/libstore/build.cc:2321:45: error: non-constant-expression cannot be narrowed from type 'int' to 'scmp_datum_t' (aka 'unsigned long') in initializer list [-Wc++11-narrowing]
EAs/ACLs are not part of the NAR canonicalisation. Worse, setting an
ACL allows a builder to create writable files in the Nix store. So get
rid of them.
Closes#185.
This prevents builders from setting the S_ISUID or S_ISGID bits,
preventing users from using a nixbld* user to create a setuid/setgid
binary to interfere with subsequent builds under the same nixbld* uid.
This is based on aszlig's seccomp code
(47f587700d).
Reported by Linus Heckemann.
Fixes
client# error: size mismatch importing path ‘/nix/store/ywf5fihjlxwijm6ygh6s0a353b5yvq4d-libidn2-0.16’; expected 0, got 120264
This is mostly an artifact of the NixOS VM test environment, where the
Nix database doesn't contain hashes/sizes.
http://hydra.nixos.org/build/53537471
And add a 116 KiB ash shell from busybox to the release build. This
helps to make sandbox builds work out of the box on non-NixOS systems
and with diverted stores.
This is useful when we're using a diverted store (e.g. "--store
local?root=/tmp/nix") in conjunction with a statically-linked sh from
the host store (e.g. "sandbox-paths =/bin/sh=/nix/store/.../bin/busybox").
Previously, if a directory `foo` existed and a file `foo-` (where `-` is any character that is sorted before `/`), then `readDirectory` would return an empty list.
To fix this, we now use a tree where we can just access the children of the node, and do not need to rely on sorting behavior to list the contents of a directory.
It now means "paths that were built locally". It no longer includes
paths that were added locally. For those we don't need info.ultimate,
since we have the content-addressability assertion (info.ca).
This is a little convenience command that opens the Nix expression of
the specified package. For example,
nix edit nixpkgs.perlPackages.Moose
opens <nixpkgs/pkgs/top-level/perl-packages.nix> in $EDITOR (at the
right line number for some editors).
This requires the package to have a meta.position attribute.
There is a security issue when a build accidentally stores its $TMPDIR
in some critical place, such as an RPATH. If
TMPDIR=/tmp/nix-build-..., then any user on the system can recreate
that directory and inject libraries into the RPATH of programs
executed by other users. Since /build probably doesn't exist (or isn't
world-writable), this mitigates the issue.
Opening an SSHStore or LegacySSHStore does not actually establish a
connection, so the try/catch block here did nothing. Added a
Store::connect() method to test whether a connection can be
established.
This is useful for one-off situations where you want to specify a
builder on the command line instead of having to mess with
nix.machines. E.g.
$ nix-build -A hello --argstr system x86_64-darwin \
--option builders 'root@macstadium1 x86_64-darwin'
will perform the specified build on "macstadium1".
It also removes the need for a separate nix.machines file since you
can specify builders in nix.conf directly. (In fact nix.machines is
yet another hack that predates the general nix.conf configuration
file, IIRC.)
Note: this option is supported by the daemon for trusted users. The
fact that this allows trusted users to specify paths to SSH keys to
which they don't normally have access is maybe a bit too much trust...
For backwards compatibility, if the URI is just a hostname, ssh://
(i.e. LegacySSHStore) is prepended automatically.
Also, all fields except the URI are now optional. For example, this is
a valid nix.machines file:
local?root=/tmp/nix
This is useful for testing the remote build machinery since you don't
have to mess around with ssh.
This is to simplify remote build configuration. These environment
variables predate nix.conf.
The build hook now has a sensible default (namely build-remote).
The current load is kept in the Nix state directory now.
Since build-remote uses buildDerivation() now, we don't need to copy
the .drv file anymore. This greatly reduces the set of input paths
copied to the remote side (e.g. from 392 to 51 store paths for GNU
hello on x86_64-darwin).
This default implementation of buildPaths() does nothing if all
requested paths are already valid, and throws an "unsupported
operation" error otherwise. This fixes a regression introduced by
c30330df6f in binary cache and legacy
SSH stores.
With catch-all rules, we hide potential errors.
It turns out that a4744254 made one cath-all useless. Flex detected that
is was impossible to reach.
The other is more subtle, as it can only trigger on unfinished escapes
in unfinished strings, which only occurs at EOF.
This caused "nix-store --import" to compute an incorrect hash on NARs
that don't fit in an unsigned int. The import would succeed, but
"nix-store --verify-path" or subsequent exports would detect an
incorrect hash.
A deeper issue is that the export/import format does not contain a
hash, so we can't detect such issues early.
Also, I learned that -Wall does not warn about this.
So for instance "nix copy --to ... nixpkgs.hello" will build
nixpkgs.hello first. It's debatable whether this is a good idea. It
seems desirable for commands like "nix copy" but maybe not for
commands like "nix path-info".
Thus
$ nix build -f foo.nix
will build foo.nix.
And
$ nix build
will build default.nix. However, this may not be a good idea because
it's kind of inconsistent, given that "nix build foo" will build the
"foo" attribute from the default installation source (i.e. the
synthesis of $NIX_PATH), rather than ./default.nix. So I may revert
this.
This allows commands like 'nix path-info', 'nix copy', 'nix verify'
etc. to work on arbitrary installables. E.g. to copy geeqie to a
binary cache:
$ nix copy -r --to file:///tmp/binary-cache nixpkgs.geeqie
Or to get the closure size of thunderbird:
$ nix path-info -S nixpkgs.thunderbird
In particular, this disallows attribute names containing dots or
starting with dots. Hydra already disallowed these. This affects the
following packages in Nixpkgs master:
2048-in-terminal
2bwm
389-ds-base
90secondportraits
lispPackages.3bmd
lispPackages.hu.dwim.asdf
lispPackages.hu.dwim.def
Closes#1342.
The typical use is to inherit Config and add Setting<T> members:
class MyClass : private Config
{
Setting<int> foo{this, 123, "foo", "the number of foos to use"};
Setting<std::string> bar{this, "blabla", "bar", "the name of the bar"};
MyClass() : Config(readConfigFile("/etc/my-app.conf"))
{
std::cout << foo << "\n"; // will print 123 unless overriden
}
};
Currently, this is used by Store and its subclasses for store
parameters. You now get a warning if you specify a non-existant store
parameter in a store URI.
This provides a significant speedup, e.g. 64 s -> 12 s for
nix-build --dry-run -I nixpkgs=channel:nixos-16.03 '<nixpkgs/nixos/tests/misc.nix>' -A test
on a cold local and CloudFront cache.
The alternative is to use lots of concurrent daemon connections but
that seems wasteful.
This is useless because the client also caches path info, and can
cause problems for long-running clients like hydra-queue-runner
(i.e. it may return cached info about paths that have been
garbage-collected).
This fixes "No such file or directory" when opening /dev/ptmx
(e.g. http://hydra.nixos.org/build/51094249).
The reason appears to be some changes to /dev/ptmx / /dev/pts handling
between Linux 4.4 and 4.9. See
https://patchwork.kernel.org/patch/7832531/.
The fix is to go back to mounting a proper /dev/pts instance inside
the sandbox. Happily, this now works inside user namespaces, even for
unprivileged users. So
NIX_REMOTE=local?root=/tmp/nix nix-build \
'<nixpkgs/nixos/tests/misc.nix>' -A test
works for non-root users.
The downside is that the fix breaks sandbox builds on older kernels
(probably pre-4.6), since mounting a devpts fails inside user
namespaces for some reason I've never been able to figure out. Builds
on those systems will fail with
error: while setting up the build environment: mounting /dev/pts: Invalid argument
Ah well.
Execute a given program with the (optional) given arguments as the
user running the evaluation, parsing stdout as an expression to be
evaluated.
There are many use cases for nix that would benefit from being able to
run arbitrary code during evaluation, including but not limited to:
* Automatic git fetching to get a sha256 from a git revision
* git rev-parse HEAD
* Automatic extraction of information from build specifications from
other tools, particularly language-specific package managers like
cabal or npm
* Secrets decryption (e.g. with nixops)
* Private repository fetching
Ideally, we would add this functionality in a more principled way to
nix, but in the mean time 'builtins.exec' can be used to get these
tasks done.
The primop is only available when the
'allow-unsafe-native-code-during-evaluation' nix option is true. That
flag also enables the 'importNative' primop, which is strictly more
powerful but less convenient (since it requires compiling a plugin
against the running version of nix).
So if "text-compression=br", the .ls file in S3 will get a
Content-Encoding of "br". Brotli appears to compress better than xz
for this kind of file and is natively supported by browsers.
You can now set the store parameter "text-compression=br" to compress
textual files in the binary cache (i.e. narinfo and logs) using
Brotli. This sets the Content-Encoding header; the extension of
compressed files is unchanged.
You can separately specify the compression of log files using
"log-compression=br". This is useful when you don't want to compress
narinfo files for backward compatibility.
Build logs on cache.nixos.org are compressed using Brotli (since this
allows them to be decompressed automatically by Chrome and Firefox),
so it's handy if "nix log" can decompress them.
This allows various Store implementations to provide different ways to
get build logs. For example, BinaryCacheStore can get the build logs
from the binary cache.
Also, remove the log-servers option since we can use substituters for
this.
* Unify SSH code in SSHStore and LegacySSHStore.
* Fix a race starting the SSH master. We now wait synchronously for
the SSH master to finish starting. This prevents the SSH clients
from starting their own connections.
* Don't use a master if max-connections == 1.
* Add a "max-connections" store parameter.
* Add a "compress" store parameter.
"build-max-jobs" and the "-j" option can now be set to "auto" to use
the number of CPUs in the system. (Unlike build-cores, it doesn't use
0 to imply auto-configuration, because a) magic values are a bad idea
in general; b) 0 is a legitimate value used to disable local
building.)
Fixes#1198.
Need to remember that std::map::insert() and emplace() don't overwrite
existing entries...
This fixes a regression relative to 1.11 that in particular triggers
in nested nix-shells.
Before:
$ nativeBuildInputs=/foo nix-shell -p hello --run 'hello'
build input /foo does not exist
After:
$ nativeBuildInputs=/foo nix-shell -p hello --run 'hello'
Hello, world!
Previously, the Settings class allowed other code to query for string
properties, which led to a proliferation of code all over the place making
up new options without any sort of central registry of valid options. This
commit pulls all those options back into the central Settings class and
removes the public get() methods, to discourage future abuses like that.
Furthermore, because we know the full set of options ahead of time, we
now fail loudly if someone enters an unrecognized option, thus preventing
subtle typos. With some template fun, we could probably also dump the full
set of options (with documentation, defaults, etc.) to the command line,
but I'm not doing that yet here.
... and use this in Downloader::downloadCached(). This fixes
$ nix-build https://nixos.org/channels/nixos-16.09-small/nixexprs.tar.xz -A hello
error: cannot import path ‘/nix/store/csfbp1s60dkgmk9f8g0zk0mwb7hzgabd-nixexprs.tar.xz’ because it lacks a valid signature
This allows <nix/fetchurl.nix> to fetch private Git/Mercurial
repositories, e.g.
import <nix/fetchurl.nix> {
url = https://edolstra@bitbucket.org/edolstra/my-private-repo/get/80a14018daed.tar.bz2;
sha256 = "1mgqzn7biqkq3hf2697b0jc4wabkqhmzq2srdymjfa6sb9zb6qs7";
}
where /etc/nix/netrc contains:
machine bitbucket.org
login edolstra
password blabla...
This works even when sandboxing is enabled.
To do: add unpacking support (i.e. fetchzip functionality).
Some sites (e.g. BitBucket) give a helpful 401 error when trying to
download a private archive if the User-Agent contains "curl", but give
a redirect to a login page otherwise (so for instance
"nix-prefetch-url" will succeed but produce useless output).
This adds support for s3:// URIs in all places where Nix allows URIs,
e.g. in builtins.fetchurl, builtins.fetchTarball, <nix/fetchurl.nix>
and NIX_PATH. It allows fetching resources from private S3 buckets,
using credentials obtained from the standard places (i.e. AWS_*
environment variables, ~/.aws/credentials and the EC2 metadata
server). This may not be super-useful in general, but since we already
depend on aws-sdk-cpp, it's a cheap feature to add.
Currently, 'nix-daemon --stdio' is always failing for me, due to the
splice call always failing with (on a 32-bit host):
splice(0, NULL, 3, NULL, 4294967295, SPLICE_F_MOVE) = -1 EINVAL (Invalid argument)
With a bit of ftracing (and luck) the problem seems to be that splice()
always fails with EINVAL if the len cast as ssize_t is negative:
http://lxr.free-electrons.com/source/fs/read_write.c?v=4.4#L384
So use SSIZE_MAX instead of SIZE_MAX.
Because config.h can #define things like _FILE_OFFSET_BITS=64 and not
every compilation unit includes config.h, we currently compile half of
Nix with _FILE_OFFSET_BITS=64 and other half with _FILE_OFFSET_BITS
unset. This causes major havoc with the Settings class on e.g. 32-bit ARM,
where different compilation units disagree with the struct layout.
E.g.:
diff --git a/src/libstore/globals.cc b/src/libstore/globals.cc
@@ -166,6 +166,8 @@ void Settings::update()
_get(useSubstitutes, "build-use-substitutes");
+ fprintf(stderr, "at Settings::update(): &useSubstitutes = %p\n", &nix::settings.useSubstitutes);
_get(buildUsersGroup, "build-users-group");
diff --git a/src/libstore/remote-store.cc b/src/libstore/remote-store.cc
+++ b/src/libstore/remote-store.cc
@@ -138,6 +138,8 @@ void RemoteStore::initConnection(Connection & conn)
void RemoteStore::setOptions(Connection & conn)
{
+ fprintf(stderr, "at RemoteStore::setOptions(): &useSubstitutes = %p\n", &nix::settings.useSubstitutes);
conn.to << wopSetOptions
Gave me:
at Settings::update(): &useSubstitutes = 0xb6e5c5cb
at RemoteStore::setOptions(): &useSubstitutes = 0xb6e5c5c7
That was not a fun one to debug!
This writes info about every path in the closure in the same format as
‘nix path-info --json’. Thus it also includes NAR hashes and sizes.
Example:
[
{
"path": "/nix/store/10h6li26i7g6z3mdpvra09yyf10mmzdr-hello-2.10",
"narHash": "sha256:0ckdc4z20kkmpqdilx0wl6cricxv90lh85xpv2qljppcmz6vzcxl",
"narSize": 197648,
"references": [
"/nix/store/10h6li26i7g6z3mdpvra09yyf10mmzdr-hello-2.10",
"/nix/store/27binbdy296qvjycdgr1535v8872vz3z-glibc-2.24"
],
"closureSize": 20939776
},
{
"path": "/nix/store/27binbdy296qvjycdgr1535v8872vz3z-glibc-2.24",
"narHash": "sha256:1nfn3m3p98y1c0kd0brp80dn9n5mycwgrk183j17rajya0h7gax3",
"narSize": 20742128,
"references": [
"/nix/store/27binbdy296qvjycdgr1535v8872vz3z-glibc-2.24"
],
"closureSize": 20742128
}
]
Fixes#1134.
Previously, all derivation attributes had to be coerced into strings
so that they could be passed via the environment. This is lossy
(e.g. lists get flattened, necessitating configureFlags
vs. configureFlagsArray, of which the latter cannot be specified as an
attribute), doesn't support attribute sets at all, and has size
limitations (necessitating hacks like passAsFile).
This patch adds a new mode for passing attributes to builders, namely
encoded as a JSON file ".attrs.json" in the current directory of the
builder. This mode is activated via the special attribute
__structuredAttrs = true;
(The idea is that one day we can set this in stdenv.mkDerivation.)
For example,
stdenv.mkDerivation {
__structuredAttrs = true;
name = "foo";
buildInputs = [ pkgs.hello pkgs.cowsay ];
doCheck = true;
hardening.format = false;
}
results in a ".attrs.json" file containing (sans the indentation):
{
"buildInputs": [],
"builder": "/nix/store/ygl61ycpr2vjqrx775l1r2mw1g2rb754-bash-4.3-p48/bin/bash",
"configureFlags": [
"--with-foo",
"--with-bar=1 2"
],
"doCheck": true,
"hardening": {
"format": false
},
"name": "foo",
"nativeBuildInputs": [
"/nix/store/10h6li26i7g6z3mdpvra09yyf10mmzdr-hello-2.10",
"/nix/store/4jnvjin0r6wp6cv1hdm5jbkx3vinlcvk-cowsay-3.03"
],
"propagatedBuildInputs": [],
"propagatedNativeBuildInputs": [],
"stdenv": "/nix/store/f3hw3p8armnzy6xhd4h8s7anfjrs15n2-stdenv",
"system": "x86_64-linux"
}
"passAsFile" is ignored in this mode because it's not needed - large
strings are included directly in the JSON representation.
It is up to the builder to do something with the JSON
representation. For example, in bash-based builders, lists/attrsets of
string values could be mapped to bash (associative) arrays.
This closes a long-time bug that allowed builds to hang Nix
indefinitely (regardless of timeouts) simply by doing
exec > /dev/null 2>&1; while true; do true; done
Now, on EOF, we just send SIGKILL to the child to make sure it's
really gone.
This allows other threads to install callbacks that run in a regular,
non-signal context. In particular, we can use this to signal the
downloader thread to quit.
Closes#1183.
Regression from a5f2750e ("Fix early removal of rc-file for nix-shell").
The removal of BASH_ENV causes nothing to be executed by bash if it
detects itself in a non-interactive context. Instead, just
use the same condition used by bash to launch bash differently.
According to bash sources, the condition (stdin and stder both
must be TTYs) is specified by POSIX so this should be pretty
safe to rely on.
Fixes#1171 on master, needs a backport to the Perl code in 1.11.
I had observed that 'bash --rcfile' would do nothing in a
non-interactive context and cause nothing to be executed if a script
using nix-shell shebangs were run in a non-interactive context.
The 'args' variable here is shadowing one in the outer scope and its
contents end up unused. This causes any '#! nix-shell' lines to
effectively be ignored. The intention here was to clear the args vector,
as far as I can tell (and it seems to work).
It failed with
AWS error uploading ‘6gaxphsyhg66mz0a00qghf9nqf7majs2.ls.xz’: Unable to parse ExceptionName: MissingContentLength Message: You must provide the Content-Length HTTP header.
possibly because the istringstream_nocopy introduced in
0d2ebb4373 doesn't supply the seek
method that the AWS library expects. So bring back the old version,
but only for S3BinaryCacheStore.
That is, when build-repeat > 0, and the output of two rounds differ,
then print a warning rather than fail the build. This is primarily to
let Hydra check reproducibility of all packages.
Jörg Thalheim
Linus Heckemann