Created
February 7, 2013 20:34
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Efficiently read arbitrary directories of an arbitrary git revision from a git repo into memory, without affecting the working directory.
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# BEWARE! This code is largely untested and not ready for production! | |
Result = Struct.new(:entries, :raw_error, :status) | |
class Entry | |
HeaderUnpackFormat = "Z100A8A8A8A12A12A8aZ100A6A2Z32Z32A8A8Z155".freeze | |
EmptyString = "".freeze | |
OctalFields = [1,2,3,4,5,6,10,13,14] | |
def self.from_stream(io) | |
header = io.read(512) | |
return nil unless header | |
fields = header.unpack(HeaderUnpackFormat) | |
OctalFields.each do |octal_field| | |
fields[octal_field] = fields[octal_field].oct | |
end | |
new(fields, io.read(fields[4])) | |
end | |
attr_reader :name | |
attr_reader :mode | |
attr_reader :uid | |
attr_reader :gid | |
attr_reader :size | |
attr_reader :mtime | |
attr_reader :checksum | |
attr_reader :typeflag | |
attr_reader :linkname | |
attr_reader :magic | |
attr_reader :version | |
attr_reader :uname | |
attr_reader :gname | |
attr_reader :devmajor | |
attr_reader :devminor | |
attr_reader :prefix | |
attr_reader :data | |
def initialize(fields, data) | |
@name = fields[0] | |
@mode = fields[1] | |
@uid = fields[2] | |
@gid = fields[3] | |
@size = fields[4] | |
@mtime = fields[5] | |
@checksum = fields[6] | |
@typeflag = fields[7] | |
@linkname = fields[8] | |
@magic = fields[9] | |
@version = fields[10] | |
@uname = fields[11] | |
@gname = fields[12] | |
@devmajor = fields[13] | |
@devminor = fields[14] | |
@prefix = fields[15] | |
@data = data | |
end | |
def skip | |
(512 - (size % 512)) % 512 | |
end | |
def full_name | |
if @prefix != EmptyString | |
File.join(@prefix, @name) | |
else | |
@name | |
end | |
end | |
end | |
def git_archive_entries(revision, *paths) | |
sor,sow = IO.pipe | |
ser,sew = IO.pipe | |
pid = Process.spawn('git', 'archive', '--format=tar', revision, *paths, out: sow, err: sew) | |
sew.close | |
sow.close | |
entries = [] | |
while entry=Entry.from_stream(sor) | |
entries << entry | |
sor.read(entry.skip) | |
end | |
stderr = ser.read | |
_, status = Process.wait2(pid) | |
Result.new(entries, stderr, status) | |
end | |
revision = 'version-2.8.0-beta' | |
paths = ['config/locales'] | |
result = git_archive_entries(revision, *paths) |
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