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nixpkgs/pkgs/build-support/fetchhg/nix-prefetch-hg
aszlig f83af95f8a
build-support: Use mktemp -d in nix-prefetch-*.
Instead of relying on $$ to not collide with an existing path.

Quoting the Bash manual about $$:

> Expands to the process ID of the shell. In a () subshell, it expands
> to the process ID of the current shell, not the subshell.

So, this is different from $BASHPID:

> Expands to the process ID of the current bash process. This differs
> from $$ under certain circumstances, such as subshells that do not
> require bash to be re-initialized.

But even $BASHPID is prone to race conditions if the process IDs wrap
around, so to be on the safe side, we're using mktemp here.

Closes #3784.

Signed-off-by: aszlig <aszlig@redmoonstudios.org>
2014-08-25 15:28:55 +02:00

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#! /bin/sh -e
url=$1
rev=$2
expHash=$3
hashType=$NIX_HASH_ALGO
if test -z "$hashType"; then
hashType=sha256
fi
if test -z "$hashFormat"; then
hashFormat=--base32
fi
if test -z "$url"; then
echo "syntax: nix-prefetch-hg URL [rev [EXPECTED-HASH]]" >&2
exit 1
fi
test -n "$rev" || rev="tip"
# If the hash was given, a file with that hash may already be in the
# store.
if test -n "$expHash"; then
finalPath=$(nix-store --print-fixed-path --recursive "$hashType" "$expHash" hg-archive)
if ! nix-store --check-validity "$finalPath" 2> /dev/null; then
finalPath=
fi
hash=$expHash
fi
# If we don't know the hash or a path with that hash doesn't exist,
# download the file and add it to the store.
if test -z "$finalPath"; then
tmpPath="$(mktemp --tmpdir -d hg-checkout-tmp-XXXXXXXX)"
trap "rm -rf \"$tmpPath\"" EXIT
tmpArchive="$tmpPath/hg-archive"
# Perform the checkout.
if [[ $url != /* ]]; then
tmpClone=$tmpPath/hg-clone
hg clone -q -y -U "$url" $tmpClone >&2
else
tmpClone=$url
fi
hg archive -q -y -r "$rev" --cwd $tmpClone $tmpArchive
rm -f $tmpArchive/.hg_archival.txt
echo "hg revision is $(cd $tmpClone; hg id -r "$rev" -i)"
# Compute the hash.
hash=$(nix-hash --type $hashType $hashFormat $tmpArchive)
if ! test -n "$QUIET"; then echo "hash is $hash" >&2; fi
# Add the downloaded file to the Nix store.
finalPath=$(nix-store --add-fixed --recursive "$hashType" $tmpArchive)
if test -n "$expHash" -a "$expHash" != "$hash"; then
echo "hash mismatch for URL \`$url'"
exit 1
fi
fi
if ! test -n "$QUIET"; then echo "path is $finalPath" >&2; fi
echo $hash
if test -n "$PRINT_PATH"; then
echo $finalPath
fi