Documentation/technical/partial-clone.txt - jrn/git - Git at Google

 Partial Clone Design Notes
 ==========================

 The "Partial Clone" feature is a performance optimization for Git that
 allows Git to function without having a complete copy of the repository.
 The goal of this work is to allow Git better handle extremely large
 repositories.

 During clone and fetch operations, Git downloads the complete contents
 and history of the repository.  This includes all commits, trees, and
 blobs for the complete life of the repository.  For extremely large
 repositories, clones can take hours (or days) and consume 100+GiB of disk
 space.

 Often in these repositories there are many blobs and trees that the user
 does not need such as:

   1. files outside of the user's work area in the tree.  For example, in
      a repository with 500K directories and 3.5M files in every commit,
      we can avoid downloading many objects if the user only needs a
      narrow "cone" of the source tree.

   2. large binary assets.  For example, in a repository where large build
      artifacts are checked into the tree, we can avoid downloading all
      previous versions of these non-mergeable binary assets and only
      download versions that are actually referenced.

 Partial clone allows us to avoid downloading such unneeded objects *in
 advance* during clone and fetch operations and thereby reduce download
 times and disk usage.  Missing objects can later be "demand fetched"
 if/when needed.

 A remote that can later provide the missing objects is called a
 promisor remote, as it promises to send the objects when
 requested. Initially Git supported only one promisor remote, the origin
 remote from which the user cloned and that was configured in the
 "extensions.partialClone" config option. Later support for more than
 one promisor remote has been implemented.

 Use of partial clone requires that the user be online and the origin
 remote or other promisor remotes be available for on-demand fetching
 of missing objects.  This may or may not be problematic for the user.
 For example, if the user can stay within the pre-selected subset of
 the source tree, they may not encounter any missing objects.
 Alternatively, the user could try to pre-fetch various objects if they
 know that they are going offline.


 Non-Goals
 ---------

 Partial clone is a mechanism to limit the number of blobs and trees downloaded
 *within* a given range of commits -- and is therefore independent of and not
 intended to conflict with existing DAG-level mechanisms to limit the set of
 requested commits (i.e. shallow clone, single branch, or fetch '<refspec>').


 Design Overview
 ---------------

 Partial clone logically consists of the following parts:

 - A mechanism for the client to describe unneeded or unwanted objects to
   the server.

 - A mechanism for the server to omit such unwanted objects from packfiles
   sent to the client.

 - A mechanism for the client to gracefully handle missing objects (that
   were previously omitted by the server).

 - A mechanism for the client to backfill missing objects as needed.


 Design Details
 --------------

 - A new pack-protocol capability "filter" is added to the fetch-pack and
   upload-pack negotiation.
 +
 This uses the existing capability discovery mechanism.
 See "filter" in linkgit:gitprotocol-pack[5].

 - Clients pass a "filter-spec" to clone and fetch which is passed to the
   server to request filtering during packfile construction.
 +
 There are various filters available to accommodate different situations.
 See "--filter=<filter-spec>" in Documentation/rev-list-options.txt.

 - On the server pack-objects applies the requested filter-spec as it
   creates "filtered" packfiles for the client.
 +
 These filtered packfiles are *incomplete* in the traditional sense because
 they may contain objects that reference objects not contained in the
 packfile and that the client doesn't already have.  For example, the
 filtered packfile may contain trees or tags that reference missing blobs
 or commits that reference missing trees.

 - On the client these incomplete packfiles are marked as "promisor packfiles"
   and treated differently by various commands.

 - On the client a repository extension is added to the local config to
   prevent older versions of git from failing mid-operation because of
   missing objects that they cannot handle.
   See "extensions.partialClone" in Documentation/technical/repository-version.txt"


 Handling Missing Objects
 ------------------------

 - An object may be missing due to a partial clone or fetch, or missing
   due to repository corruption.  To differentiate these cases, the
   local repository specially indicates such filtered packfiles
   obtained from promisor remotes as "promisor packfiles".
 +
 These promisor packfiles consist of a "<name>.promisor" file with
 arbitrary contents (like the "<name>.keep" files), in addition to
 their "<name>.pack" and "<name>.idx" files.

 - The local repository considers a "promisor object" to be an object that
   it knows (to the best of its ability) that promisor remotes have promised
   that they have, either because the local repository has that object in one of
   its promisor packfiles, or because another promisor object refers to it.
 +
 When Git encounters a missing object, Git can see if it is a promisor object
 and handle it appropriately.  If not, Git can report a corruption.
 +
 This means that there is no need for the client to explicitly maintain an
 expensive-to-modify list of missing objects.[a]

 - Since almost all Git code currently expects any referenced object to be
   present locally and because we do not want to force every command to do
   a dry-run first, a fallback mechanism is added to allow Git to attempt
   to dynamically fetch missing objects from promisor remotes.
 +
 When the normal object lookup fails to find an object, Git invokes
 promisor_remote_get_direct() to try to get the object from a promisor
 remote and then retry the object lookup.  This allows objects to be
 "faulted in" without complicated prediction algorithms.
 +
 For efficiency reasons, no check as to whether the missing object is
 actually a promisor object is performed.
 +
 Dynamic object fetching tends to be slow as objects are fetched one at
 a time.

 - `checkout` (and any other command using `unpack-trees`) has been taught
   to bulk pre-fetch all required missing blobs in a single batch.

 - `rev-list` has been taught to print missing objects.
 +
 This can be used by other commands to bulk prefetch objects.
 For example, a "git log -p A..B" may internally want to first do
 something like "git rev-list --objects --quiet --missing=print A..B"
 and prefetch those objects in bulk.

 - `fsck` has been updated to be fully aware of promisor objects.

 - `repack` in GC has been updated to not touch promisor packfiles at all,
   and to only repack other objects.

 - The global variable "fetch_if_missing" is used to control whether an
   object lookup will attempt to dynamically fetch a missing object or
   report an error.
 +
 We are not happy with this global variable and would like to remove it,
 but that requires significant refactoring of the object code to pass an
 additional flag.


 Fetching Missing Objects
 ------------------------

 - Fetching of objects is done by invoking a "git fetch" subprocess.

 - The local repository sends a request with the hashes of all requested
   objects, and does not perform any packfile negotiation.
   It then receives a packfile.

 - Because we are reusing the existing fetch mechanism, fetching
   currently fetches all objects referred to by the requested objects, even
   though they are not necessary.

 - Fetching with `--refetch` will request a complete new filtered packfile from
   the remote, which can be used to change a filter without needing to
   dynamically fetch missing objects.

 Using many promisor remotes
 ---------------------------

 Many promisor remotes can be configured and used.

 This allows for example a user to have multiple geographically-close
 cache servers for fetching missing blobs while continuing to do
 filtered `git-fetch` commands from the central server.

 When fetching objects, promisor remotes are tried one after the other
 until all the objects have been fetched.

 Remotes that are considered "promisor" remotes are those specified by
 the following configuration variables:

 - `extensions.partialClone = <name>`

 - `remote.<name>.promisor = true`

 - `remote.<name>.partialCloneFilter = ...`

 Only one promisor remote can be configured using the
 `extensions.partialClone` config variable. This promisor remote will
 be the last one tried when fetching objects.

 We decided to make it the last one we try, because it is likely that
 someone using many promisor remotes is doing so because the other
 promisor remotes are better for some reason (maybe they are closer or
 faster for some kind of objects) than the origin, and the origin is
 likely to be the remote specified by extensions.partialClone.

 This justification is not very strong, but one choice had to be made,
 and anyway the long term plan should be to make the order somehow
 fully configurable.

 For now though the other promisor remotes will be tried in the order
 they appear in the config file.

 Current Limitations
 -------------------

 - It is not possible to specify the order in which the promisor
   remotes are tried in other ways than the order in which they appear
   in the config file.
 +
 It is also not possible to specify an order to be used when fetching
 from one remote and a different order when fetching from another
 remote.

 - It is not possible to push only specific objects to a promisor
   remote.
 +
 It is not possible to push at the same time to multiple promisor
 remote in a specific order.

 - Dynamic object fetching will only ask promisor remotes for missing
   objects.  We assume that promisor remotes have a complete view of the
   repository and can satisfy all such requests.

 - Repack essentially treats promisor and non-promisor packfiles as 2
   distinct partitions and does not mix them.

 - Dynamic object fetching invokes fetch-pack once *for each item*
   because most algorithms stumble upon a missing object and need to have
   it resolved before continuing their work.  This may incur significant
   overhead -- and multiple authentication requests -- if many objects are
   needed.

 - Dynamic object fetching currently uses the existing pack protocol V0
   which means that each object is requested via fetch-pack.  The server
   will send a full set of info/refs when the connection is established.
   If there are large number of refs, this may incur significant overhead.


 Future Work
 -----------

 - Improve the way to specify the order in which promisor remotes are
   tried.
 +
 For example this could allow to specify explicitly something like:
 "When fetching from this remote, I want to use these promisor remotes
 in this order, though, when pushing or fetching to that remote, I want
 to use those promisor remotes in that order."

 - Allow pushing to promisor remotes.
 +
 The user might want to work in a triangular work flow with multiple
 promisor remotes that each have an incomplete view of the repository.

 - Allow non-pathname-based filters to make use of packfile bitmaps (when
   present).  This was just an omission during the initial implementation.

 - Investigate use of a long-running process to dynamically fetch a series
   of objects, such as proposed in [5,6] to reduce process startup and
   overhead costs.
 +
 It would be nice if pack protocol V2 could allow that long-running
 process to make a series of requests over a single long-running
 connection.

 - Investigate pack protocol V2 to avoid the info/refs broadcast on
   each connection with the server to dynamically fetch missing objects.

 - Investigate the need to handle loose promisor objects.
 +
 Objects in promisor packfiles are allowed to reference missing objects
 that can be dynamically fetched from the server.  An assumption was
 made that loose objects are only created locally and therefore should
 not reference a missing object.  We may need to revisit that assumption
 if, for example, we dynamically fetch a missing tree and store it as a
 loose object rather than a single object packfile.
 +
 This does not necessarily mean we need to mark loose objects as promisor;
 it may be sufficient to relax the object lookup or is-promisor functions.


 Non-Tasks
 ---------

 - Every time the subject of "demand loading blobs" comes up it seems
   that someone suggests that the server be allowed to "guess" and send
   additional objects that may be related to the requested objects.
 +
 No work has gone into actually doing that; we're just documenting that
 it is a common suggestion.  We're not sure how it would work and have
 no plans to work on it.
 +
 It is valid for the server to send more objects than requested (even
 for a dynamic object fetch), but we are not building on that.


 Footnotes
 ---------

 [a] expensive-to-modify list of missing objects:  Earlier in the design of
     partial clone we discussed the need for a single list of missing objects.
     This would essentially be a sorted linear list of OIDs that the were
     omitted by the server during a clone or subsequent fetches.

 This file would need to be loaded into memory on every object lookup.
 It would need to be read, updated, and re-written (like the .git/index)
 on every explicit "git fetch" command *and* on any dynamic object fetch.

 The cost to read, update, and write this file could add significant
 overhead to every command if there are many missing objects.  For example,
 if there are 100M missing blobs, this file would be at least 2GiB on disk.

 With the "promisor" concept, we *infer* a missing object based upon the
 type of packfile that references it.


 Related Links
 -------------
 [0] https://crbug.com/git/2
     Bug#2: Partial Clone

 [1] https://lore.kernel.org/git/20170113155253.1644-1-benpeart@microsoft.com/ +
     Subject: [RFC] Add support for downloading blobs on demand +
     Date: Fri, 13 Jan 2017 10:52:53 -0500

 [2] https://lore.kernel.org/git/cover.1506714999.git.jonathantanmy@google.com/ +
     Subject: [PATCH 00/18] Partial clone (from clone to lazy fetch in 18 patches) +
     Date: Fri, 29 Sep 2017 13:11:36 -0700

 [3] https://lore.kernel.org/git/20170426221346.25337-1-jonathantanmy@google.com/ +
     Subject: Proposal for missing blob support in Git repos +
     Date: Wed, 26 Apr 2017 15:13:46 -0700

 [4] https://lore.kernel.org/git/1488999039-37631-1-git-send-email-git@jeffhostetler.com/ +
     Subject: [PATCH 00/10] RFC Partial Clone and Fetch +
     Date: Wed,  8 Mar 2017 18:50:29 +0000

 [5] https://lore.kernel.org/git/20170505152802.6724-1-benpeart@microsoft.com/ +
     Subject: [PATCH v7 00/10] refactor the filter process code into a reusable module +
     Date: Fri,  5 May 2017 11:27:52 -0400

 [6] https://lore.kernel.org/git/20170714132651.170708-1-benpeart@microsoft.com/ +
     Subject: [RFC/PATCH v2 0/1] Add support for downloading blobs on demand +
     Date: Fri, 14 Jul 2017 09:26:50 -0400
	Partial Clone Design Notes
	==========================

	The "Partial Clone" feature is a performance optimization for Git that
	allows Git to function without having a complete copy of the repository.
	The goal of this work is to allow Git better handle extremely large
	repositories.

	During clone and fetch operations, Git downloads the complete contents
	and history of the repository. This includes all commits, trees, and
	blobs for the complete life of the repository. For extremely large
	repositories, clones can take hours (or days) and consume 100+GiB of disk
	space.

	Often in these repositories there are many blobs and trees that the user
	does not need such as:

	1. files outside of the user's work area in the tree. For example, in
	a repository with 500K directories and 3.5M files in every commit,
	we can avoid downloading many objects if the user only needs a
	narrow "cone" of the source tree.

	2. large binary assets. For example, in a repository where large build
	artifacts are checked into the tree, we can avoid downloading all
	previous versions of these non-mergeable binary assets and only
	download versions that are actually referenced.

	Partial clone allows us to avoid downloading such unneeded objects *in
	advance* during clone and fetch operations and thereby reduce download
	times and disk usage. Missing objects can later be "demand fetched"
	if/when needed.

	A remote that can later provide the missing objects is called a
	promisor remote, as it promises to send the objects when
	requested. Initially Git supported only one promisor remote, the origin
	remote from which the user cloned and that was configured in the
	"extensions.partialClone" config option. Later support for more than
	one promisor remote has been implemented.

	Use of partial clone requires that the user be online and the origin
	remote or other promisor remotes be available for on-demand fetching
	of missing objects. This may or may not be problematic for the user.
	For example, if the user can stay within the pre-selected subset of
	the source tree, they may not encounter any missing objects.
	Alternatively, the user could try to pre-fetch various objects if they
	know that they are going offline.


	Non-Goals
	---------

	Partial clone is a mechanism to limit the number of blobs and trees downloaded
	within a given range of commits -- and is therefore independent of and not
	intended to conflict with existing DAG-level mechanisms to limit the set of
	requested commits (i.e. shallow clone, single branch, or fetch '<refspec>').


	Design Overview
	---------------

	Partial clone logically consists of the following parts:

	- A mechanism for the client to describe unneeded or unwanted objects to
	the server.

	- A mechanism for the server to omit such unwanted objects from packfiles
	sent to the client.

	- A mechanism for the client to gracefully handle missing objects (that
	were previously omitted by the server).

	- A mechanism for the client to backfill missing objects as needed.


	Design Details
	--------------

	- A new pack-protocol capability "filter" is added to the fetch-pack and
	upload-pack negotiation.
	+
	This uses the existing capability discovery mechanism.
	See "filter" in linkgit:gitprotocol-pack[5].

	- Clients pass a "filter-spec" to clone and fetch which is passed to the
	server to request filtering during packfile construction.
	+
	There are various filters available to accommodate different situations.
	See "--filter=<filter-spec>" in Documentation/rev-list-options.txt.

	- On the server pack-objects applies the requested filter-spec as it
	creates "filtered" packfiles for the client.
	+
	These filtered packfiles are incomplete in the traditional sense because
	they may contain objects that reference objects not contained in the
	packfile and that the client doesn't already have. For example, the
	filtered packfile may contain trees or tags that reference missing blobs
	or commits that reference missing trees.

	- On the client these incomplete packfiles are marked as "promisor packfiles"
	and treated differently by various commands.

	- On the client a repository extension is added to the local config to
	prevent older versions of git from failing mid-operation because of
	missing objects that they cannot handle.
	See "extensions.partialClone" in Documentation/technical/repository-version.txt"


	Handling Missing Objects
	------------------------

	- An object may be missing due to a partial clone or fetch, or missing
	due to repository corruption. To differentiate these cases, the
	local repository specially indicates such filtered packfiles
	obtained from promisor remotes as "promisor packfiles".
	+
	These promisor packfiles consist of a "<name>.promisor" file with
	arbitrary contents (like the "<name>.keep" files), in addition to
	their "<name>.pack" and "<name>.idx" files.

	- The local repository considers a "promisor object" to be an object that
	it knows (to the best of its ability) that promisor remotes have promised
	that they have, either because the local repository has that object in one of
	its promisor packfiles, or because another promisor object refers to it.
	+
	When Git encounters a missing object, Git can see if it is a promisor object
	and handle it appropriately. If not, Git can report a corruption.
	+
	This means that there is no need for the client to explicitly maintain an
	expensive-to-modify list of missing objects.[a]

	- Since almost all Git code currently expects any referenced object to be
	present locally and because we do not want to force every command to do
	a dry-run first, a fallback mechanism is added to allow Git to attempt
	to dynamically fetch missing objects from promisor remotes.
	+
	When the normal object lookup fails to find an object, Git invokes
	promisor_remote_get_direct() to try to get the object from a promisor
	remote and then retry the object lookup. This allows objects to be
	"faulted in" without complicated prediction algorithms.
	+
	For efficiency reasons, no check as to whether the missing object is
	actually a promisor object is performed.
	+
	Dynamic object fetching tends to be slow as objects are fetched one at
	a time.

	- `checkout` (and any other command using `unpack-trees`) has been taught
	to bulk pre-fetch all required missing blobs in a single batch.

	- `rev-list` has been taught to print missing objects.
	+
	This can be used by other commands to bulk prefetch objects.
	For example, a "git log -p A..B" may internally want to first do
	something like "git rev-list --objects --quiet --missing=print A..B"
	and prefetch those objects in bulk.

	- `fsck` has been updated to be fully aware of promisor objects.

	- `repack` in GC has been updated to not touch promisor packfiles at all,
	and to only repack other objects.

	- The global variable "fetch_if_missing" is used to control whether an
	object lookup will attempt to dynamically fetch a missing object or
	report an error.
	+
	We are not happy with this global variable and would like to remove it,
	but that requires significant refactoring of the object code to pass an
	additional flag.


	Fetching Missing Objects
	------------------------

	- Fetching of objects is done by invoking a "git fetch" subprocess.

	- The local repository sends a request with the hashes of all requested
	objects, and does not perform any packfile negotiation.
	It then receives a packfile.

	- Because we are reusing the existing fetch mechanism, fetching
	currently fetches all objects referred to by the requested objects, even
	though they are not necessary.

	- Fetching with `--refetch` will request a complete new filtered packfile from
	the remote, which can be used to change a filter without needing to
	dynamically fetch missing objects.

	Using many promisor remotes
	---------------------------

	Many promisor remotes can be configured and used.

	This allows for example a user to have multiple geographically-close
	cache servers for fetching missing blobs while continuing to do
	filtered `git-fetch` commands from the central server.

	When fetching objects, promisor remotes are tried one after the other
	until all the objects have been fetched.

	Remotes that are considered "promisor" remotes are those specified by
	the following configuration variables:

	- `extensions.partialClone = <name>`

	- `remote.<name>.promisor = true`

	- `remote.<name>.partialCloneFilter = ...`

	Only one promisor remote can be configured using the
	`extensions.partialClone` config variable. This promisor remote will
	be the last one tried when fetching objects.

	We decided to make it the last one we try, because it is likely that
	someone using many promisor remotes is doing so because the other
	promisor remotes are better for some reason (maybe they are closer or
	faster for some kind of objects) than the origin, and the origin is
	likely to be the remote specified by extensions.partialClone.

	This justification is not very strong, but one choice had to be made,
	and anyway the long term plan should be to make the order somehow
	fully configurable.

	For now though the other promisor remotes will be tried in the order
	they appear in the config file.

	Current Limitations
	-------------------

	- It is not possible to specify the order in which the promisor
	remotes are tried in other ways than the order in which they appear
	in the config file.
	+
	It is also not possible to specify an order to be used when fetching
	from one remote and a different order when fetching from another
	remote.

	- It is not possible to push only specific objects to a promisor
	remote.
	+
	It is not possible to push at the same time to multiple promisor
	remote in a specific order.

	- Dynamic object fetching will only ask promisor remotes for missing
	objects. We assume that promisor remotes have a complete view of the
	repository and can satisfy all such requests.

	- Repack essentially treats promisor and non-promisor packfiles as 2
	distinct partitions and does not mix them.

	- Dynamic object fetching invokes fetch-pack once for each item
	because most algorithms stumble upon a missing object and need to have
	it resolved before continuing their work. This may incur significant
	overhead -- and multiple authentication requests -- if many objects are
	needed.

	- Dynamic object fetching currently uses the existing pack protocol V0
	which means that each object is requested via fetch-pack. The server
	will send a full set of info/refs when the connection is established.
	If there are large number of refs, this may incur significant overhead.


	Future Work
	-----------

	- Improve the way to specify the order in which promisor remotes are
	tried.
	+
	For example this could allow to specify explicitly something like:
	"When fetching from this remote, I want to use these promisor remotes
	in this order, though, when pushing or fetching to that remote, I want
	to use those promisor remotes in that order."

	- Allow pushing to promisor remotes.
	+
	The user might want to work in a triangular work flow with multiple
	promisor remotes that each have an incomplete view of the repository.

	- Allow non-pathname-based filters to make use of packfile bitmaps (when
	present). This was just an omission during the initial implementation.

	- Investigate use of a long-running process to dynamically fetch a series
	of objects, such as proposed in [5,6] to reduce process startup and
	overhead costs.
	+
	It would be nice if pack protocol V2 could allow that long-running
	process to make a series of requests over a single long-running
	connection.

	- Investigate pack protocol V2 to avoid the info/refs broadcast on
	each connection with the server to dynamically fetch missing objects.

	- Investigate the need to handle loose promisor objects.
	+
	Objects in promisor packfiles are allowed to reference missing objects
	that can be dynamically fetched from the server. An assumption was
	made that loose objects are only created locally and therefore should
	not reference a missing object. We may need to revisit that assumption
	if, for example, we dynamically fetch a missing tree and store it as a
	loose object rather than a single object packfile.
	+
	This does not necessarily mean we need to mark loose objects as promisor;
	it may be sufficient to relax the object lookup or is-promisor functions.


	Non-Tasks
	---------

	- Every time the subject of "demand loading blobs" comes up it seems
	that someone suggests that the server be allowed to "guess" and send
	additional objects that may be related to the requested objects.
	+
	No work has gone into actually doing that; we're just documenting that
	it is a common suggestion. We're not sure how it would work and have
	no plans to work on it.
	+
	It is valid for the server to send more objects than requested (even
	for a dynamic object fetch), but we are not building on that.


	Footnotes
	---------

	[a] expensive-to-modify list of missing objects: Earlier in the design of
	partial clone we discussed the need for a single list of missing objects.
	This would essentially be a sorted linear list of OIDs that the were
	omitted by the server during a clone or subsequent fetches.

	This file would need to be loaded into memory on every object lookup.
	It would need to be read, updated, and re-written (like the .git/index)
	on every explicit "git fetch" command and on any dynamic object fetch.

	The cost to read, update, and write this file could add significant
	overhead to every command if there are many missing objects. For example,
	if there are 100M missing blobs, this file would be at least 2GiB on disk.

	With the "promisor" concept, we infer a missing object based upon the
	type of packfile that references it.


	Related Links
	-------------
	[0] https://crbug.com/git/2
	Bug#2: Partial Clone

	[1] https://lore.kernel.org/git/20170113155253.1644-1-benpeart@microsoft.com/ +
	Subject: [RFC] Add support for downloading blobs on demand +
	Date: Fri, 13 Jan 2017 10:52:53 -0500

	[2] https://lore.kernel.org/git/cover.1506714999.git.jonathantanmy@google.com/ +
	Subject: [PATCH 00/18] Partial clone (from clone to lazy fetch in 18 patches) +
	Date: Fri, 29 Sep 2017 13:11:36 -0700

	[3] https://lore.kernel.org/git/20170426221346.25337-1-jonathantanmy@google.com/ +
	Subject: Proposal for missing blob support in Git repos +
	Date: Wed, 26 Apr 2017 15:13:46 -0700

	[4] https://lore.kernel.org/git/1488999039-37631-1-git-send-email-git@jeffhostetler.com/ +
	Subject: [PATCH 00/10] RFC Partial Clone and Fetch +
	Date: Wed, 8 Mar 2017 18:50:29 +0000

	[5] https://lore.kernel.org/git/20170505152802.6724-1-benpeart@microsoft.com/ +
	Subject: [PATCH v7 00/10] refactor the filter process code into a reusable module +
	Date: Fri, 5 May 2017 11:27:52 -0400

	[6] https://lore.kernel.org/git/20170714132651.170708-1-benpeart@microsoft.com/ +
	Subject: [RFC/PATCH v2 0/1] Add support for downloading blobs on demand +
	Date: Fri, 14 Jul 2017 09:26:50 -0400