Merge branch 'ds/commit-graph-fsck' into jt/commit-graph-per-object-store

* ds/commit-graph-fsck: (23 commits)
  coccinelle: update commit.cocci
  commit-graph: update design document
  gc: automatically write commit-graph files
  commit-graph: add '--reachable' option
  commit-graph: use string-list API for input
  fsck: verify commit-graph
  commit-graph: verify contents match checksum
  commit-graph: test for corrupted octopus edge
  commit-graph: verify commit date
  commit-graph: verify generation number
  commit-graph: verify parent list
  commit-graph: verify root tree OIDs
  commit-graph: verify objects exist
  commit-graph: verify corrupt OID fanout and lookup
  commit-graph: verify required chunks are present
  commit-graph: verify catches corrupt signature
  commit-graph: add 'verify' subcommand
  commit-graph: load a root tree from specific graph
  commit: force commit to parse from object database
  commit-graph: parse commit from chosen graph
  ...

5 files changed, 25 insertions, 27 deletions

diff --git a/Documentation/config.txt b/Documentation/config.txt
index 1cc18a828ca..978deecfeee 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -904,9 +904,12 @@ core.notesRef::
 This setting defaults to "refs/notes/commits", and it can be overridden by
 the `GIT_NOTES_REF` environment variable.  See linkgit:git-notes[1].
 
-core.commitGraph::
-	Enable git commit graph feature. Allows reading from the
-	commit-graph file.
+gc.commitGraph::
+	If true, then gc will rewrite the commit-graph file when
+	linkgit:git-gc[1] is run. When using linkgit:git-gc[1]
+	'--auto' the commit-graph will be updated if housekeeping is
+	required. Default is false. See linkgit:git-commit-graph[1]
+	for details.
 
 core.sparseCheckout::
 	Enable "sparse checkout" feature. See section "Sparse checkout" in
diff --git a/Documentation/git-commit-graph.txt b/Documentation/git-commit-graph.txt
index 4c97b555cca..dececb79d77 100644
--- a/Documentation/git-commit-graph.txt
+++ b/Documentation/git-commit-graph.txt
@@ -10,6 +10,7 @@ SYNOPSIS
 --------
 [verse]
 'git commit-graph read' [--object-dir <dir>]
+'git commit-graph verify' [--object-dir <dir>]
 'git commit-graph write' <options> [--object-dir <dir>]
 
 
@@ -37,12 +38,16 @@ Write a commit graph file based on the commits found in packfiles.
 +
 With the `--stdin-packs` option, generate the new commit graph by
 walking objects only in the specified pack-indexes. (Cannot be combined
-with --stdin-commits.)
+with `--stdin-commits` or `--reachable`.)
 +
 With the `--stdin-commits` option, generate the new commit graph by
 walking commits starting at the commits specified in stdin as a list
 of OIDs in hex, one OID per line. (Cannot be combined with
---stdin-packs.)
+`--stdin-packs` or `--reachable`.)
++
+With the `--reachable` option, generate the new commit graph by walking
+commits starting at all refs. (Cannot be combined with `--stdin-commits`
+or `--stdin-packs`.)
 +
 With the `--append` option, include all commits that are present in the
 existing commit-graph file.
@@ -52,6 +57,11 @@ existing commit-graph file.
 Read a graph file given by the commit-graph file and output basic
 details about the graph file. Used for debugging purposes.
 
+'verify'::
+
+Read the commit-graph file and verify its contents against the object
+database. Used to check for corrupted data.
+
 
 EXAMPLES
 --------
diff --git a/Documentation/git-fsck.txt b/Documentation/git-fsck.txt
index b9f060e3b20..ab9a93fb9b8 100644
--- a/Documentation/git-fsck.txt
+++ b/Documentation/git-fsck.txt
@@ -110,6 +110,9 @@ Any corrupt objects you will have to find in backups or other archives
 (i.e., you can just remove them and do an 'rsync' with some other site in
 the hopes that somebody else has the object you have corrupted).
 
+If core.commitGraph is true, the commit-graph file will also be inspected
+using 'git commit-graph verify'. See linkgit:git-commit-graph[1].
+
 Extracted Diagnostics
 ---------------------
 
diff --git a/Documentation/git-gc.txt b/Documentation/git-gc.txt
index 24b2dd44fe4..f5bc98ccb36 100644
--- a/Documentation/git-gc.txt
+++ b/Documentation/git-gc.txt
@@ -136,6 +136,10 @@ The optional configuration variable `gc.packRefs` determines if
 it within all non-bare repos or it can be set to a boolean value.
 This defaults to true.
 
+The optional configuration variable `gc.commitGraph` determines if
+'git gc' should run 'git commit-graph write'. This can be set to a
+boolean value. This defaults to false.
+
 The optional configuration variable `gc.aggressiveWindow` controls how
 much time is spent optimizing the delta compression of the objects in
 the repository when the --aggressive option is specified.  The larger
diff --git a/Documentation/technical/commit-graph.txt b/Documentation/technical/commit-graph.txt
index e1a883eb462..c664acbd765 100644
--- a/Documentation/technical/commit-graph.txt
+++ b/Documentation/technical/commit-graph.txt
@@ -118,9 +118,6 @@ Future Work
 - The commit graph feature currently does not honor commit grafts. This can
   be remedied by duplicating or refactoring the current graft logic.
 
-- The 'commit-graph' subcommand does not have a "verify" mode that is
-  necessary for integration with fsck.
-
 - After computing and storing generation numbers, we must make graph
   walks aware of generation numbers to gain the performance benefits they
   enable. This will mostly be accomplished by swapping a commit-date-ordered
@@ -130,25 +127,6 @@ Future Work
     - 'log --topo-order'
     - 'tag --merged'
 
-- Currently, parse_commit_gently() requires filling in the root tree
-  object for a commit. This passes through lookup_tree() and consequently
-  lookup_object(). Also, it calls lookup_commit() when loading the parents.
-  These method calls check the ODB for object existence, even if the
-  consumer does not need the content. For example, we do not need the
-  tree contents when computing merge bases. Now that commit parsing is
-  removed from the computation time, these lookup operations are the
-  slowest operations keeping graph walks from being fast. Consider
-  loading these objects without verifying their existence in the ODB and
-  only loading them fully when consumers need them. Consider a method
-  such as "ensure_tree_loaded(commit)" that fully loads a tree before
-  using commit->tree.
-
-- The current design uses the 'commit-graph' subcommand to generate the graph.
-  When this feature stabilizes enough to recommend to most users, we should
-  add automatic graph writes to common operations that create many commits.
-  For example, one could compute a graph on 'clone', 'fetch', or 'repack'
-  commands.
-
 - A server could provide a commit graph file as part of the network protocol
   to avoid extra calculations by clients. This feature is only of benefit if
   the user is willing to trust the file, because verifying the file is correct