[PATCH v2 4/4] git-p4: add support for large file systems

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From: Lars Schneider <larsxschneider@xxxxxxxxx>

Perforce repositories can contain large (binary) files. Migrating these
repositories to Git generates very large local clones. External storage
systems such as LFS [1] or git-annex [2] try to address this problem.

Add a generic mechanism to detect large files based on extension,
uncompressed size, and/or compressed size. Add LFS as example
implementation.

[1] https://git-lfs.github.com/
[2] http://www.git-annex.org/

Signed-off-by: Lars Schneider <larsxschneider@xxxxxxxxx>
---
 Documentation/git-p4.txt |  21 ++++
 git-p4.py                | 126 +++++++++++++++++++++--
 t/t9823-git-p4-lfs.sh    | 263 +++++++++++++++++++++++++++++++++++++++++++++++
 3 files changed, 401 insertions(+), 9 deletions(-)
 create mode 100755 t/t9823-git-p4-lfs.sh

diff --git a/Documentation/git-p4.txt b/Documentation/git-p4.txt
index 82aa5d6..eac5bad 100644
--- a/Documentation/git-p4.txt
+++ b/Documentation/git-p4.txt
@@ -510,6 +510,27 @@ git-p4.useClientSpec::
 	option '--use-client-spec'.  See the "CLIENT SPEC" section above.
 	This variable is a boolean, not the name of a p4 client.
 
+git-p4.largeFileSystem::
+	Specify the system that is used used for large (binary) files. Only
+	"LFS" [1] is supported right now. Download and install the Git LFS
+	command line extension to use this option.
+	[1] https://git-lfs.github.com/
+
+git-p4.largeFileExtensions::
+	All files matching a file extension in the list will be processed
+	by the large file system. Do not prefix the extensions with '.'.
+
+git-p4.largeFileThreshold::
+	All files with an uncompressed size exceeding the threshold will be
+	processed by the large file system. By default the threshold is
+	defined in bytes. Add the suffix k, m, or g to change the unit.
+
+git-p4.largeFileCompressedThreshold::
+	All files with an compressed size exceeding the threshold will be
+	processed by the large file system. This option might significantly
+	slow down your clone/sync process. By default the threshold is
+	defined in bytes. Add the suffix k, m, or g to change the unit.
+
 Submit variables
 ~~~~~~~~~~~~~~~~
 git-p4.detectRenames::
diff --git a/git-p4.py b/git-p4.py
index 4d78e1c..cde75a5 100755
--- a/git-p4.py
+++ b/git-p4.py
@@ -22,6 +22,8 @@ import platform
 import re
 import shutil
 import stat
+import zipfile
+import zlib
 
 try:
     from subprocess import CalledProcessError
@@ -922,6 +924,51 @@ def wildcard_present(path):
     m = re.search("[*#@%]", path)
     return m is not None
 
+def largeFileSystem():
+    try:
+        return getattr(sys.modules[__name__], gitConfig('git-p4.largeFileSystem'))
+    except AttributeError as e:
+        die('Large file system not supported: %s' % gitConfig('git-p4.largeFileSystem'))
+
+class LFS:
+    @staticmethod
+    def description():
+        return 'LFS (see https://git-lfs.github.com/)'
+
+    @staticmethod
+    def attributeFilter():
+        return 'lfs'
+
+    @staticmethod
+    def generatePointer(cloneDestination, relPath, contents):
+        # Write P4 content to temp file
+        p4ContentTempFile = tempfile.NamedTemporaryFile(prefix='git-p4-large-file', delete=False)
+        for d in contents:
+            p4ContentTempFile.write(d)
+        p4ContentTempFile.flush()
+
+        # Generate LFS pointer file based on P4 content
+        lfsProcess = subprocess.Popen(
+            ['git', 'lfs', 'pointer', '--file=' + p4ContentTempFile.name],
+            stdout=subprocess.PIPE
+        )
+        lfsPointerFile = lfsProcess.stdout.read()
+        if lfsProcess.wait():
+            os.remove(p4ContentTempFile.name)
+            die('git-lfs command failed. Did you install the extension?')
+        contents = [i+'\n' for i in lfsPointerFile.split('\n')[2:][:-1]]
+
+        # Write P4 content to LFS
+        oid = contents[1].split(' ')[1].split(':')[1][:-1]
+        oidPath = os.path.join(cloneDestination, '.git', 'lfs', 'objects', oid[:2], oid[2:4])
+        if not os.path.isdir(oidPath):
+            os.makedirs(oidPath)
+        shutil.move(p4ContentTempFile.name, os.path.join(oidPath, oid))
+
+        # LFS Spec states that pointer files should not have the executable bit set.
+        gitMode = '100644'
+        return (gitMode, contents)
+
 class Command:
     def __init__(self):
         self.usage = "usage: %prog [options]"
@@ -2038,6 +2085,7 @@ class P4Sync(Command, P4UserMap):
         self.clientSpecDirs = None
         self.tempBranches = []
         self.tempBranchLocation = "git-p4-tmp"
+        self.largeFiles = []
 
         if gitConfig("git-p4.syncFromOrigin") == "false":
             self.syncWithOrigin = False
@@ -2158,6 +2206,59 @@ class P4Sync(Command, P4UserMap):
 
         return branches
 
+    def writeToGitStream(self, gitMode, relPath, contents):
+        self.gitStream.write('M %s inline %s\n' % (gitMode, relPath))
+        self.gitStream.write('data %d\n' % sum(len(d) for d in contents))
+        for d in contents:
+            self.gitStream.write(d)
+        self.gitStream.write('\n')
+
+    def writeGitAttributesToStream(self):
+        self.writeToGitStream(
+            '100644',
+            '.gitattributes',
+            [
+                '\n',
+                '#\n',
+                '# %s\n' % largeFileSystem().description(),
+                '#\n',
+            ] +
+            ['*.' + f.replace(' ', '[:space:]') + ' filter=%s -text\n' % largeFileSystem().attributeFilter()
+                for f in gitConfigList("git-p4.largeFileExtensions")
+            ] +
+            ['/' + f.replace(' ', '[:space:]') + ' filter=%s -text\n' % largeFileSystem().attributeFilter()
+                for f in self.largeFiles if not self.hasLargeFileExtension(f)
+            ]
+        )
+
+    def hasLargeFileExtension(self, relPath):
+        return reduce(
+            lambda a, b: a or b,
+            [relPath.endswith('.' + e) for e in gitConfigList('git-p4.largeFileExtensions')],
+            False
+        )
+
+    def exceedsLargeFileThreshold(self, relPath, contents):
+        if gitConfigInt('git-p4.largeFileThreshold'):
+            contentsSize = sum(len(d) for d in contents)
+            if contentsSize > gitConfigInt('git-p4.largeFileThreshold'):
+                return True
+        if gitConfigInt('git-p4.largeFileCompressedThreshold'):
+            contentFile = tempfile.NamedTemporaryFile(prefix='git-p4-large-file', delete=False)
+            for d in contents:
+                contentFile.write(d)
+            contentFile.flush()
+            compressedContentFile = tempfile.NamedTemporaryFile(prefix='git-p4-large-file', delete=False)
+            zf = zipfile.ZipFile(compressedContentFile.name, mode='w')
+            zf.write(contentFile.name, compress_type=zipfile.ZIP_DEFLATED)
+            zf.close()
+            compressedContentsSize = zf.infolist()[0].compress_size
+            os.remove(contentFile.name)
+            os.remove(compressedContentFile.name)
+            if compressedContentsSize > gitConfigInt('git-p4.largeFileCompressedThreshold'):
+                return True
+        return False
+
     # output one file from the P4 stream
     # - helper for streamP4Files
 
@@ -2226,17 +2327,20 @@ class P4Sync(Command, P4UserMap):
             text = regexp.sub(r'$\1$', text)
             contents = [ text ]
 
-        self.gitStream.write("M %s inline %s\n" % (git_mode, relPath))
+        if relPath == '.gitattributes':
+            die('.gitattributes already exists in P4.')
 
-        # total length...
-        length = 0
-        for d in contents:
-            length = length + len(d)
+        if (gitConfig('git-p4.largeFileSystem') and
+            (   self.exceedsLargeFileThreshold(relPath, contents) or
+                self.hasLargeFileExtension(relPath)
+            )):
+            (git_mode, contents) = largeFileSystem().generatePointer(self.cloneDestination, relPath, contents)
+            self.largeFiles.append(relPath)
+            self.writeGitAttributesToStream()
+            if verbose:
+                sys.stderr.write("%s added to large file system\n" % relPath)
 
-        self.gitStream.write("data %d\n" % length)
-        for d in contents:
-            self.gitStream.write(d)
-        self.gitStream.write("\n")
+        self.writeToGitStream(git_mode, relPath, contents)
 
     def streamOneP4Deletion(self, file):
         relPath = self.stripRepoPath(file['path'], self.branchPrefixes)
@@ -2244,6 +2348,10 @@ class P4Sync(Command, P4UserMap):
             sys.stderr.write("delete %s\n" % relPath)
         self.gitStream.write("D %s\n" % relPath)
 
+        if relPath in self.largeFiles:
+            self.largeFiles.remove(relPath)
+            self.writeGitAttributesToStream()
+
     # handle another chunk of streaming data
     def streamP4FilesCb(self, marshalled):
 
diff --git a/t/t9823-git-p4-lfs.sh b/t/t9823-git-p4-lfs.sh
new file mode 100755
index 0000000..a7587bf
--- /dev/null
+++ b/t/t9823-git-p4-lfs.sh
@@ -0,0 +1,263 @@
+#!/bin/sh
+
+test_description='Clone repositories and store files in LFS'
+
+git lfs help >/dev/null 2>&1 || {
+	skip_all='skipping git p4 LFS tests; no git lfs'
+	test_done
+}
+
+. ./lib-git-p4.sh
+
+test_file_in_lfs() {
+	FILE=$1
+	SIZE=$2
+	EXPECTED_CONTENT=$3
+	test_path_is_file $FILE &&
+	test_line_count = 3 $FILE &&
+	cat $FILE | grep "size $SIZE" &&
+	HASH=$(cat $FILE | grep "oid sha256:" | sed -e 's/oid sha256://g') &&
+	LFS_FILE=".git/lfs/objects/${HASH:0:2}/${HASH:2:2}/$HASH"
+	test_path_is_file $LFS_FILE &&
+	echo $EXPECTED_CONTENT >expect
+	test_cmp expect $LFS_FILE
+}
+
+test_expect_success 'start p4d' '
+	start_p4d
+'
+
+test_expect_success 'Create repo with binary files' '
+	client_view "//depot/... //client/..." &&
+	(
+		cd "$cli" &&
+
+		echo "txt 7b" >file1.txt &&
+		p4 add file1.txt &&
+		echo "bin 13 bytes" >file2.dat &&
+		p4 add file2.dat &&
+		p4 submit -d "Add text and binary file" &&
+
+		mkdir "path with spaces" &&
+		echo "bin 13 bytes" >"path with spaces/file3.bin" &&
+		p4 add "path with spaces/file3.bin" &&
+		p4 submit -d "Add another binary file with same content and spaces in path" &&
+
+		echo "bin 14 bytesx" >file4.bin &&
+		p4 add file4.bin &&
+		p4 submit -d "Add another binary file with different content"
+	)
+'
+
+test_expect_success 'Store files in LFS based on size (>12 bytes)' '
+	client_view "//depot/... //client/..." &&
+	test_when_finished cleanup_git &&
+	(
+		cd "$git" &&
+		git init . &&
+		git config git-p4.largeFileSystem LFS &&
+		git config git-p4.largeFileThreshold 12 &&
+		git p4 clone --use-client-spec --destination="$git" //depot@all &&
+
+		test_file_in_lfs file2.dat 13 "bin 13 bytes" &&
+		test_file_in_lfs "path with spaces/file3.bin" 13 "bin 13 bytes" &&
+		test_file_in_lfs file4.bin 14 "bin 14 bytesx" &&
+
+		find ".git/lfs/objects" -type f >actual &&
+		test_line_count = 2 actual &&
+
+		cat >expect <<-\EOF &&
+
+		#
+		# LFS (see https://git-lfs.github.com/)
+		#
+		/file2.dat filter=lfs -text
+		/path[:space:]with[:space:]spaces/file3.bin filter=lfs -text
+		/file4.bin filter=lfs -text
+		EOF
+		test_path_is_file .gitattributes &&
+		test_cmp expect .gitattributes
+	)
+'
+
+test_expect_success 'Store files in LFS based on size (>13 bytes)' '
+	client_view "//depot/... //client/..." &&
+	test_when_finished cleanup_git &&
+	(
+		cd "$git" &&
+		git init . &&
+		git config git-p4.largeFileSystem LFS &&
+		git config git-p4.largeFileThreshold 13 &&
+		git p4 clone --use-client-spec --destination="$git" //depot@all &&
+
+		test_file_in_lfs file4.bin 14 "bin 14 bytesx" &&
+
+		find ".git/lfs/objects" -type f >actual &&
+		test_line_count = 1 actual &&
+
+		cat >expect <<-\EOF &&
+
+		#
+		# LFS (see https://git-lfs.github.com/)
+		#
+		/file4.bin filter=lfs -text
+		EOF
+		test_path_is_file .gitattributes &&
+		test_cmp expect .gitattributes
+	)
+'
+
+test_expect_success 'Store files in LFS based on extension (dat)' '
+	client_view "//depot/... //client/..." &&
+	test_when_finished cleanup_git &&
+	(
+		cd "$git" &&
+		git init . &&
+		git config git-p4.largeFileSystem LFS &&
+		git config git-p4.largeFileExtensions dat &&
+		git p4 clone --use-client-spec --destination="$git" //depot@all &&
+
+		test_file_in_lfs file2.dat 13 "bin 13 bytes" &&
+
+		find ".git/lfs/objects" -type f >actual &&
+		test_line_count = 1 actual &&
+
+		cat >expect <<-\EOF &&
+
+		#
+		# LFS (see https://git-lfs.github.com/)
+		#
+		*.dat filter=lfs -text
+		EOF
+		test_path_is_file .gitattributes &&
+		test_cmp expect .gitattributes
+	)
+'
+
+test_expect_success 'Store files in LFS based on size (>13 bytes) and extension (dat)' '
+	client_view "//depot/... //client/..." &&
+	test_when_finished cleanup_git &&
+	(
+		cd "$git" &&
+		git init . &&
+		git config git-p4.largeFileSystem LFS &&
+		git config git-p4.largeFileExtensions dat &&
+		git config git-p4.largeFileThreshold 13 &&
+		git p4 clone --use-client-spec --destination="$git" //depot@all &&
+
+		test_file_in_lfs file2.dat 13 "bin 13 bytes" &&
+		test_file_in_lfs file4.bin 14 "bin 14 bytesx" &&
+
+		find ".git/lfs/objects" -type f >actual &&
+		test_line_count = 2 actual &&
+
+		cat >expect <<-\EOF &&
+
+		#
+		# LFS (see https://git-lfs.github.com/)
+		#
+		*.dat filter=lfs -text
+		/file4.bin filter=lfs -text
+		EOF
+		test_path_is_file .gitattributes &&
+		test_cmp expect .gitattributes
+	)
+'
+
+test_expect_success 'Remove file from repo and store files in LFS based on size (>12 bytes)' '
+	client_view "//depot/... //client/..." &&
+	(
+		cd "$cli" &&
+		p4 delete file4.bin &&
+		p4 submit -d "Remove file"
+	) &&
+
+	client_view "//depot/... //client/..." &&
+	test_when_finished cleanup_git &&
+	(
+		cd "$git" &&
+		git init . &&
+		git config git-p4.largeFileSystem LFS &&
+		git config git-p4.largeFileThreshold 12 &&
+		git p4 clone --use-client-spec --destination="$git" //depot@all &&
+
+		test_file_in_lfs file2.dat 13 "bin 13 bytes" &&
+		test_file_in_lfs "path with spaces/file3.bin" 13 "bin 13 bytes" &&
+		! test_path_is_file file4.bin &&
+
+		find ".git/lfs/objects" -type f >actual &&
+		# 3 is correct here as some commits in the tree still reference the deleted file
+		test_line_count = 3 actual
+
+		cat >expect <<-\EOF &&
+
+		#
+		# LFS (see https://git-lfs.github.com/)
+		#
+		/file2.dat filter=lfs -text
+		/path[:space:]with[:space:]spaces/file3.bin filter=lfs -text
+		EOF
+		test_path_is_file .gitattributes &&
+		test_cmp expect .gitattributes
+	)
+'
+
+test_expect_success 'Add big files to repo and store files in LFS based on compressed size (>19 bytes)' '
+	client_view "//depot/... //client/..." &&
+	(
+		cd "$cli" &&
+		echo "bin 24 bytesxxxxxxxxxxx" >file5.bin &&
+		p4 add file5.bin &&
+		p4 submit -d "Add another binary file with different content" &&
+
+		echo "bin 34 bytesxxxxxxxxxxxzzzzzzzzzz" >file6.bin &&
+		p4 add file6.bin &&
+		p4 submit -d "Add another binary file with different content"
+	) &&
+
+	client_view "//depot/... //client/..." &&
+	test_when_finished cleanup_git &&
+	(
+		cd "$git" &&
+		git init . &&
+		git config git-p4.largeFileSystem LFS &&
+		git config git-p4.largeFileCompressedThreshold 19 &&
+		# We only import HEAD here ("@all" is missing!)
+		git p4 clone --use-client-spec --destination="$git" //depot &&
+
+		test_file_in_lfs file6.bin 13 "bin 34 bytesxxxxxxxxxxxzzzzzzzzzz" &&
+
+		find ".git/lfs/objects" -type f >actual &&
+		test_line_count = 1 actual
+
+		cat >expect <<-\EOF &&
+
+		#
+		# LFS (see https://git-lfs.github.com/)
+		#
+		/file6.bin filter=lfs -text
+		EOF
+		test_path_is_file .gitattributes &&
+		test_cmp expect .gitattributes
+	)
+'
+
+test_expect_success 'Clone repo with existing .gitattributes file' '
+	client_view "//depot/... //client/..." &&
+	(
+		cd "$cli" &&
+
+		echo "*.txt text" >.gitattributes &&
+		p4 add .gitattributes &&
+		p4 submit -d "Add .gitattributes"
+	) &&
+
+	test_must_fail git p4 clone --use-client-spec --destination="$git" //depot 2>errs &&
+	grep ".gitattributes already exists in P4." errs
+'
+
+test_expect_success 'kill p4d' '
+	kill_p4d
+'
+
+test_done
-- 
1.9.5 (Apple Git-50.3)

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