[Buildroot] [PATCH 13/13] download: git: introduce cache feature

[Arnout Vandecappelle <arnout@mind.be>]

On 27-10-17 20:28, Peter Seiderer wrote:
> Hello Maxime,
> 
> On Tue,  4 Jul 2017 18:22:11 +0200, Maxime Hadjinlian <maxime.hadjinlian@gmail.com> wrote:
> 
>> Now we keep the git clone that we download and generates our tarball
>> from there.
> 
> For my Raspberry testcase with 'BR2_LINUX_KERNEL_CUSTOM_REPO_URL="https://github.com/raspberrypi/linux.git"'
> the cloned git repository is downloaded as 'dl/linux/git'.
> 
> This will lead to collisions e.g. for 'https://github.com/hardkernel/linux.git'.
> 
> I think a better approach would be to store the git clone under the complete
> source url (escaped), e.g. 'github-com-raspberrypi-linux-git' or
> 'github_com_raspberrypi_linux.git'?

 No, that's exactly what we want. When the full history has to be downloaded,
90% of the objects in a linux tree are the same and can be reused, even for
wildly different vendor trees. And even if they are completely different
packages that happen to have the same name, then it is still not a problem that
they are the same.

 The only possible problem is that there may be conflicting tags with the same
name and different content. Therefore, it is essential that we still do a fetch
every time, even if the tag that we're looking for is already there, to be sure
that we are looking at the right tag.

 Regards,
 Arnout

> 
> Regards,
> Peter
> 
>> The main goal here is that if you change the version of a package (say
>> Linux), instead of cloning all over again, you will simply 'git fetch'
>> from the repo the missing objects, then generates the tarball again.
>>
>> This should speed the 'source' part of the build significantly.
>>
>> The drawback is that the DL_DIR will grow much larger; but time is more
>> important than disk space nowadays.
>>
>> Signed-off-by: Maxime Hadjinlian <maxime.hadjinlian@gmail.com>
>> ---
>>  support/download/git | 69 ++++++++++++++++++++++++++++++----------------------
>>  1 file changed, 40 insertions(+), 29 deletions(-)
>>
>> diff --git a/support/download/git b/support/download/git
>> index a49e448e60..834345b53a 100755
>> --- a/support/download/git
>> +++ b/support/download/git
>> @@ -39,28 +39,34 @@ _git() {
>>      eval ${GIT} "${@}"
>>  }
>>  
>> -# Try a shallow clone, since it is faster than a full clone - but that only
>> -# works if the version is a ref (tag or branch). Before trying to do a shallow
>> -# clone we check if ${cset} is in the list provided by git ls-remote. If not
>> -# we fall back on a full clone.
>> -#
>> -# Messages for the type of clone used are provided to ease debugging in case of
>> -# problems
>> -git_done=0
>> -if [ -n "$(_git ls-remote "'${uri}'" "'${cset}'" 2>&1)" ]; then
>> -    printf "Doing shallow clone\n"
>> -    if _git clone ${verbose} "${@}" --depth 1 -b "'${cset}'" "'${uri}'" "'${basename}'"; then
>> -        git_done=1
>> -    else
>> -        printf "Shallow clone failed, falling back to doing a full clone\n"
>> +# We want to check if a cache of the git clone of this repo already exists.
>> +git_cache="${BR2_DL_DIR}/${basename%%-*}/git"
>> +
>> +# If the cache directory already exists, don't try to clone.
>> +if [ ! -d "${git_cache}" ]; then
>> +    # Try a shallow clone, since it is faster than a full clone - but that
>> +    # only works if the versionis a ref (tag or branch). Before trying to do a
>> +    # shallow clone we check if ${cset} is in the list provided by git
>> +    # ls-remote. If not we fall back on a full clone.
>> +    #
>> +    # Messages for the type of clone used are provided to ease debugging in
>> +    # case of problems
>> +    git_done=0
>> +    if [ -n "$(_git ls-remote "'${uri}'" "'${cset}'" 2>&1)" ]; then
>> +        printf "Doing shallow clone\n"
>> +        if _git clone ${verbose} "${@}" --depth 1 -b "'${cset}'" "'${uri}'" "'${git_cache}'"; then
>> +            git_done=1
>> +        else
>> +            printf "Shallow clone failed, falling back to doing a full clone\n"
>> +        fi
>> +    fi
>> +    if [ ${git_done} -eq 0 ]; then
>> +        printf "Doing full clone\n"
>> +        _git clone ${verbose} "${@}" "'${uri}'" "'${git_cache}'"
>>      fi
>> -fi
>> -if [ ${git_done} -eq 0 ]; then
>> -    printf "Doing full clone\n"
>> -    _git clone ${verbose} "${@}" "'${uri}'" "'${basename}'"
>>  fi
>>  
>> -pushd "${basename}" >/dev/null
>> +pushd "${git_cache}" >/dev/null
>>  
>>  # Try to get the special refs exposed by some forges (pull-requests for
>>  # github, changes for gerrit...). There is no easy way to know whether
>> @@ -86,20 +92,25 @@ if [ ${recurse} -eq 1 ]; then
>>      _git submodule update --init --recursive
>>  fi
>>  
>> -# We do not want the .git dir; we keep other .git files, in case they
>> -# are the only files in their directory.
>> +# Generate the archive, sort with the C locale so that it is reproducible
>> +# We do not want the .git dir; we keep other .git
>> +# files, in case they are the only files in their directory.
>>  # The .git dir would generate non reproducible tarballs as it depends on
>>  # the state of the remote server. It also would generate large tarballs
>>  # (gigabytes for some linux trees) when a full clone took place.
>> -rm -rf .git
>> +find . -not -type d \
>> +	-and -not -path "./.git/*" >"${BR2_DL_DIR}/${basename}.list"
>> +LC_ALL=C sort <"${BR2_DL_DIR}/${basename}.list" >"${BR2_DL_DIR}/${basename}.list.sorted"
>>  
>> -popd >/dev/null
>> -
>> -# Generate the archive, sort with the C locale so that it is reproducible
>> -find "${basename}" -not -type d >"${basename}.list"
>> -LC_ALL=C sort <"${basename}.list" >"${basename}.list.sorted"
>>  # Create GNU-format tarballs, since that's the format of the tarballs on
>>  # sources.buildroot.org and used in the *.hash files
>> -tar cf - --numeric-owner --owner=0 --group=0 --mtime="${date}" --format=gnu \
>> -         -T "${basename}.list.sorted" >"${output}.tar"
>> +tar cf - --transform="s/^\./${basename}/" \
>> +	--numeric-owner --owner=0 --group=0 --mtime="${date}" --format=gnu \
>> +         -T "${BR2_DL_DIR}/${basename}.list.sorted" >"${output}.tar"
>>  gzip -n <"${output}.tar" >"${output}"
>> +tar tf "${output}"
>> +
>> +rm -f "${BR2_DL_DIR}/${basename}.list"
>> +rm -f "${BR2_DL_DIR}/${basename}.list.sorted"
>> +
>> +popd >/dev/null
> 

-- 
Arnout Vandecappelle                          arnout at mind be
Senior Embedded Software Architect            +32-16-286500
Essensium/Mind                                http://www.mind.be
G.Geenslaan 9, 3001 Leuven, Belgium           BE 872 984 063 RPR Leuven
LinkedIn profile: http://www.linkedin.com/in/arnoutvandecappelle
GPG fingerprint:  7493 020B C7E3 8618 8DEC 222C 82EB F404 F9AC 0DDF