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-rw-r--r--Documentation/RelNotes/2.18.0.txt122
-rw-r--r--Documentation/SubmittingPatches4
-rw-r--r--Documentation/config.txt3
-rw-r--r--Documentation/diff-options.txt4
-rw-r--r--Documentation/git-bisect.txt4
-rw-r--r--Documentation/git-fetch-pack.txt2
-rw-r--r--Documentation/git-filter-branch.txt8
-rw-r--r--Documentation/git-for-each-ref.txt2
-rw-r--r--Documentation/git-gc.txt28
-rw-r--r--Documentation/git-mktree.txt2
-rw-r--r--Documentation/git-rebase.txt7
-rw-r--r--Documentation/git-send-email.txt18
-rw-r--r--Documentation/git-shortlog.txt2
-rw-r--r--Documentation/git-stash.txt2
-rw-r--r--Documentation/git-status.txt2
-rw-r--r--Documentation/git-svn.txt13
-rw-r--r--Documentation/git-worktree.txt18
-rw-r--r--Documentation/gitrepository-layout.txt5
-rw-r--r--Documentation/howto/recover-corrupted-object-harder.txt2
-rw-r--r--Documentation/technical/api-directory-listing.txt2
-rw-r--r--Documentation/technical/api-object-access.txt2
-rw-r--r--Documentation/technical/hash-function-transition.txt40
22 files changed, 228 insertions, 64 deletions
diff --git a/Documentation/RelNotes/2.18.0.txt b/Documentation/RelNotes/2.18.0.txt
new file mode 100644
index 0000000000..5f16516734
--- /dev/null
+++ b/Documentation/RelNotes/2.18.0.txt
@@ -0,0 +1,122 @@
+Git 2.18 Release Notes
+======================
+
+Updates since v2.17
+-------------------
+
+UI, Workflows & Features
+
+ * Rename detection logic in "diff" family that is used in "merge" has
+ learned to guess when all of x/a, x/b and x/c have moved to z/a,
+ z/b and z/c, it is likely that x/d added in the meantime would also
+ want to move to z/d by taking the hint that the entire directory
+ 'x' moved to 'z'. A bug causing dirty files involved in a rename
+ to be overwritten during merge has also been fixed as part of this
+ work.
+
+ * "git filter-branch" learned to use a different exit code to allow
+ the callers to tell the case where there was no new commits to
+ rewrite from other error cases.
+
+ * When built with more recent cURL, GIT_SSL_VERSION can now specify
+ "tlsv1.3" as its value.
+
+
+Performance, Internal Implementation, Development Support etc.
+
+ * A "git fetch" from a repository with insane number of refs into a
+ repository that is already up-to-date still wasted too many cycles
+ making many lstat(2) calls to see if these objects at the tips
+ exist as loose objects locally. These lstat(2) calls are optimized
+ away by enumerating all loose objects beforehand.
+ It is unknown if the new strategy negatively affects existing use
+ cases, fetching into a repository with many loose objects from a
+ repository with small number of refs.
+
+ * Git can be built to use either v1 or v2 of the PCRE library, and so
+ far, the build-time configuration USE_LIBPCRE=YesPlease instructed
+ the build procedure to use v1, but now it means v2. USE_LIBPCRE1
+ and USE_LIBPCRE2 can be used to explicitly choose which version to
+ use, as before.
+
+ * The build procedure learned to optionally use symbolic links
+ (instead of hardlinks and copies) to install "git-foo" for built-in
+ commands, whose binaries are all identical.
+
+ * Conversion from uchar[20] to struct object_id continues.
+
+ * The way "git worktree prune" worked internally has been simplified,
+ by assuming how "git worktree move" moves an existing worktree to a
+ different place.
+
+ * Code clean-up for the "repository" abstraction.
+ (merge 00a3da2a13 nd/remove-ignore-env-field later to maint).
+
+ * Code to find the length to uniquely abbreviate object names based
+ on packfile content, which is a relatively recent addtion, has been
+ optimized to use the same fan-out table.
+
+ * The mechanism to use parse-options API to automate the command line
+ completion continues to get extended and polished.
+
+ * Copies of old scripted Porcelain commands in contrib/examples/ have
+ been removed.
+
+ * Some tests that rely on the exact hardcoded values of object names
+ have been updated in preparation for hash function migration.
+
+ * Perf-test update.
+
+ * Test helper update.
+
+ * The effort continues to refactor the internal global data structure
+ to make it possible to open multiple repositories, work with and
+ then close them,
+
+ * Small test-helper programs have been consolidated into a single
+ binary.
+
+Also contains various documentation updates and code clean-ups.
+
+
+Fixes since v2.17
+-----------------
+
+ * "git shortlog cruft" aborted with a BUG message when run outside a
+ Git repository. The command has been taught to complain about
+ extra and unwanted arguments on its command line instead in such a
+ case.
+ (merge 4aa0161e83 ma/shortlog-revparse later to maint).
+
+ * "git stash push -u -- <pathspec>" gave an unnecessary and confusing
+ error message when there was no tracked files that match the
+ <pathspec>, which has been fixed.
+ (merge 353278687e tg/stash-untracked-with-pathspec-fix later to maint).
+
+ * "git tag --contains no-such-commit" gave a full list of options
+ after giving an error message.
+ (merge 3bb0923f06 ps/contains-id-error-message later to maint).
+
+ * "diff-highlight" filter (in contrib/) learned to undertand "git log
+ --graph" output better.
+ (merge 4551fbba14 jk/diff-highlight-graph-fix later to maint).
+
+ * when refs that do not point at committish are given, "git
+ filter-branch" gave a misleading error messages. This has been
+ corrected.
+ (merge f78ab355e7 yk/filter-branch-non-committish-refs later to maint).
+
+ * "git submodule status" misbehaved on a submodule that has been
+ removed from the working tree.
+ (merge 74b6bda32f rs/status-with-removed-submodule later to maint).
+
+ * When credential helper exits very quickly without reading its
+ input, it used to cause Git to die with SIGPIPE, which has been
+ fixed.
+ (merge a0d51e8d0e eb/cred-helper-ignore-sigpipe later to maint).
+
+ * Other minor doc, test and build updates and code cleanups.
+ (merge 248f66ed8e nd/trace-with-env later to maint).
+ (merge 14ced5562c ys/bisect-object-id-missing-conversion-fix later to maint).
+ (merge 5988eb631a ab/doc-hash-brokenness later to maint).
+ (merge a4d4e32a70 pk/test-avoid-pipe-hiding-exit-status later to maint).
diff --git a/Documentation/SubmittingPatches b/Documentation/SubmittingPatches
index a1d0feca36..945f8edb46 100644
--- a/Documentation/SubmittingPatches
+++ b/Documentation/SubmittingPatches
@@ -260,8 +260,8 @@ that starts with `-----BEGIN PGP SIGNED MESSAGE-----`. That is
not a text/plain, it's something else.
Send your patch with "To:" set to the mailing list, with "cc:" listing
-people who are involved in the area you are touching (the output from
-`git blame $path` and `git shortlog --no-merges $path` would help to
+people who are involved in the area you are touching (the `git
+contacts` command in `contrib/contacts/` can help to
identify them), to solicit comments and reviews.
:1: footnote:[The current maintainer: gitster@pobox.com]
diff --git a/Documentation/config.txt b/Documentation/config.txt
index ce9102cea8..2659153cb3 100644
--- a/Documentation/config.txt
+++ b/Documentation/config.txt
@@ -1957,6 +1957,7 @@ http.sslVersion::
- tlsv1.0
- tlsv1.1
- tlsv1.2
+ - tlsv1.3
+
Can be overridden by the `GIT_SSL_VERSION` environment variable.
@@ -3364,7 +3365,7 @@ uploadpack.packObjectsHook::
stdout.
uploadpack.allowFilter::
- If this option is set, `upload-pack` will advertise partial
+ If this option is set, `upload-pack` will support partial
clone and partial fetch object filtering.
+
Note that this configuration variable is ignored if it is seen in the
diff --git a/Documentation/diff-options.txt b/Documentation/diff-options.txt
index e3a44f03cd..f466600972 100644
--- a/Documentation/diff-options.txt
+++ b/Documentation/diff-options.txt
@@ -568,7 +568,7 @@ the normal order.
--
+
Patterns have the same syntax and semantics as patterns used for
-fnmantch(3) without the FNM_PATHNAME flag, except a pathname also
+fnmatch(3) without the FNM_PATHNAME flag, except a pathname also
matches a pattern if removing any number of the final pathname
components matches the pattern. For example, the pattern "`foo*bar`"
matches "`fooasdfbar`" and "`foo/bar/baz/asdf`" but not "`foobarx`".
@@ -592,7 +592,7 @@ endif::git-format-patch[]
Treat all files as text.
--ignore-cr-at-eol::
- Ignore carrige-return at the end of line when doing a comparison.
+ Ignore carriage-return at the end of line when doing a comparison.
--ignore-space-at-eol::
Ignore changes in whitespace at EOL.
diff --git a/Documentation/git-bisect.txt b/Documentation/git-bisect.txt
index 4a1417bdcd..4b45d837a7 100644
--- a/Documentation/git-bisect.txt
+++ b/Documentation/git-bisect.txt
@@ -165,8 +165,8 @@ To get a reminder of the currently used terms, use
git bisect terms
------------------------------------------------
-You can get just the old (respectively new) term with `git bisect term
---term-old` or `git bisect term --term-good`.
+You can get just the old (respectively new) term with `git bisect terms
+--term-old` or `git bisect terms --term-good`.
If you would like to use your own terms instead of "bad"/"good" or
"new"/"old", you can choose any names you like (except existing bisect
diff --git a/Documentation/git-fetch-pack.txt b/Documentation/git-fetch-pack.txt
index f7ebe36a7b..c975884793 100644
--- a/Documentation/git-fetch-pack.txt
+++ b/Documentation/git-fetch-pack.txt
@@ -88,7 +88,7 @@ be in a separate packet, and the list must end with a flush packet.
infinite even if there is an ancestor-chain that long.
--shallow-since=<date>::
- Deepen or shorten the history of a shallow'repository to
+ Deepen or shorten the history of a shallow repository to
include all reachable commits after <date>.
--shallow-exclude=<revision>::
diff --git a/Documentation/git-filter-branch.txt b/Documentation/git-filter-branch.txt
index 3a52e4dce3..b634043183 100644
--- a/Documentation/git-filter-branch.txt
+++ b/Documentation/git-filter-branch.txt
@@ -222,6 +222,14 @@ this purpose, they are instead rewritten to point at the nearest ancestor that
was not excluded.
+EXIT STATUS
+-----------
+
+On success, the exit status is `0`. If the filter can't find any commits to
+rewrite, the exit status is `2`. On any other error, the exit status may be
+any other non-zero value.
+
+
Examples
--------
diff --git a/Documentation/git-for-each-ref.txt b/Documentation/git-for-each-ref.txt
index dffa14a795..085d177d97 100644
--- a/Documentation/git-for-each-ref.txt
+++ b/Documentation/git-for-each-ref.txt
@@ -121,7 +121,7 @@ refname::
stripping with positive <N>, or it becomes the full refname if
stripping with negative <N>. Neither is an error.
+
-`strip` can be used as a synomym to `lstrip`.
+`strip` can be used as a synonym to `lstrip`.
objecttype::
The type of the object (`blob`, `tree`, `commit`, `tag`).
diff --git a/Documentation/git-gc.txt b/Documentation/git-gc.txt
index 571b5a7e3c..3126e0dd00 100644
--- a/Documentation/git-gc.txt
+++ b/Documentation/git-gc.txt
@@ -15,8 +15,9 @@ DESCRIPTION
-----------
Runs a number of housekeeping tasks within the current repository,
such as compressing file revisions (to reduce disk space and increase
-performance) and removing unreachable objects which may have been
-created from prior invocations of 'git add'.
+performance), removing unreachable objects which may have been
+created from prior invocations of 'git add', packing refs, pruning
+reflog, rerere metadata or stale working trees.
Users are encouraged to run this task on a regular basis within
each repository to maintain good disk space utilization and good
@@ -45,20 +46,25 @@ OPTIONS
With this option, 'git gc' checks whether any housekeeping is
required; if not, it exits without performing any work.
Some git commands run `git gc --auto` after performing
- operations that could create many loose objects.
+ operations that could create many loose objects. Housekeeping
+ is required if there are too many loose objects or too many
+ packs in the repository.
+
-Housekeeping is required if there are too many loose objects or
-too many packs in the repository. If the number of loose objects
-exceeds the value of the `gc.auto` configuration variable, then
-all loose objects are combined into a single pack using
-`git repack -d -l`. Setting the value of `gc.auto` to 0
-disables automatic packing of loose objects.
+If the number of loose objects exceeds the value of the `gc.auto`
+configuration variable, then all loose objects are combined into a
+single pack using `git repack -d -l`. Setting the value of `gc.auto`
+to 0 disables automatic packing of loose objects.
+
If the number of packs exceeds the value of `gc.autoPackLimit`,
then existing packs (except those marked with a `.keep` file)
are consolidated into a single pack by using the `-A` option of
'git repack'. Setting `gc.autoPackLimit` to 0 disables
automatic consolidation of packs.
++
+If houskeeping is required due to many loose objects or packs, all
+other housekeeping tasks (e.g. rerere, working trees, reflog...) will
+be performed as well.
+
--prune=<date>::
Prune loose objects older than date (default is 2 weeks ago,
@@ -133,6 +139,10 @@ The optional configuration variable `gc.pruneExpire` controls how old
the unreferenced loose objects have to be before they are pruned. The
default is "2 weeks ago".
+Optional configuration variable `gc.worktreePruneExpire` controls how
+old a stale working tree should be before `git worktree prune` deletes
+it. Default is "3 months ago".
+
Notes
-----
diff --git a/Documentation/git-mktree.txt b/Documentation/git-mktree.txt
index c3616e7711..27fe2b32e1 100644
--- a/Documentation/git-mktree.txt
+++ b/Documentation/git-mktree.txt
@@ -14,7 +14,7 @@ SYNOPSIS
DESCRIPTION
-----------
Reads standard input in non-recursive `ls-tree` output format, and creates
-a tree object. The order of the tree entries is normalised by mktree so
+a tree object. The order of the tree entries is normalized by mktree so
pre-sorting the input is not required. The object name of the tree object
built is written to the standard output.
diff --git a/Documentation/git-rebase.txt b/Documentation/git-rebase.txt
index 3277ca1432..dd852068b1 100644
--- a/Documentation/git-rebase.txt
+++ b/Documentation/git-rebase.txt
@@ -364,9 +364,10 @@ default is `--no-fork-point`, otherwise the default is `--fork-point`.
Incompatible with the --interactive option.
--signoff::
- This flag is passed to 'git am' to sign off all the rebased
- commits (see linkgit:git-am[1]). Incompatible with the
- --interactive option.
+ Add a Signed-off-by: trailer to all the rebased commits. Note
+ that if `--interactive` is given then only commits marked to be
+ picked, edited or reworded will have the trailer added. Incompatible
+ with the `--preserve-merges` option.
-i::
--interactive::
diff --git a/Documentation/git-send-email.txt b/Documentation/git-send-email.txt
index 71ef97ba9b..60cf96f4c1 100644
--- a/Documentation/git-send-email.txt
+++ b/Documentation/git-send-email.txt
@@ -255,7 +255,7 @@ must be used for each option.
--batch-size=<num>::
Some email servers (e.g. smtp.163.com) limit the number emails to be
- sent per session (connection) and this will lead to a faliure when
+ sent per session (connection) and this will lead to a failure when
sending many messages. With this option, send-email will disconnect after
sending $<num> messages and wait for a few seconds (see --relogin-delay)
and reconnect, to work around such a limit. You may want to
@@ -473,16 +473,7 @@ edit ~/.gitconfig to specify your account settings:
If you have multifactor authentication setup on your gmail account, you will
need to generate an app-specific password for use with 'git send-email'. Visit
-https://security.google.com/settings/security/apppasswords to setup an
-app-specific password. Once setup, you can store it with the credentials
-helper:
-
- $ git credential fill
- protocol=smtp
- host=smtp.gmail.com
- username=youname@gmail.com
- password=app-password
-
+https://security.google.com/settings/security/apppasswords to create it.
Once your commits are ready to be sent to the mailing list, run the
following commands:
@@ -491,6 +482,11 @@ following commands:
$ edit outgoing/0000-*
$ git send-email outgoing/*
+The first time you run it, you will be prompted for your credentials. Enter the
+app-specific or your regular password as appropriate. If you have credential
+helper configured (see linkgit:git-credential[1]), the password will be saved in
+the credential store so you won't have to type it the next time.
+
Note: the following perl modules are required
Net::SMTP::SSL, MIME::Base64 and Authen::SASL
diff --git a/Documentation/git-shortlog.txt b/Documentation/git-shortlog.txt
index ee6c5476c1..5e35ea18ac 100644
--- a/Documentation/git-shortlog.txt
+++ b/Documentation/git-shortlog.txt
@@ -8,8 +8,8 @@ git-shortlog - Summarize 'git log' output
SYNOPSIS
--------
[verse]
-git log --pretty=short | 'git shortlog' [<options>]
'git shortlog' [<options>] [<revision range>] [[\--] <path>...]
+git log --pretty=short | 'git shortlog' [<options>]
DESCRIPTION
-----------
diff --git a/Documentation/git-stash.txt b/Documentation/git-stash.txt
index 056dfb8661..7ef8c47911 100644
--- a/Documentation/git-stash.txt
+++ b/Documentation/git-stash.txt
@@ -14,7 +14,7 @@ SYNOPSIS
'git stash' ( pop | apply ) [--index] [-q|--quiet] [<stash>]
'git stash' branch <branchname> [<stash>]
'git stash' [push [-p|--patch] [-k|--[no-]keep-index] [-q|--quiet]
- [-u|--include-untracked] [-a|--all] [-m|--message <message>]]
+ [-u|--include-untracked] [-a|--all] [-m|--message <message>]
[--] [<pathspec>...]]
'git stash' clear
'git stash' create [<message>]
diff --git a/Documentation/git-status.txt b/Documentation/git-status.txt
index 6c230c0c72..c16e27e63d 100644
--- a/Documentation/git-status.txt
+++ b/Documentation/git-status.txt
@@ -113,7 +113,7 @@ The possible options are:
- 'matching' - Shows ignored files and directories matching an
ignore pattern.
+
-When 'matching' mode is specified, paths that explicity match an
+When 'matching' mode is specified, paths that explicitly match an
ignored pattern are shown. If a directory matches an ignore pattern,
then it is shown, but not paths contained in the ignored directory. If
a directory does not match an ignore pattern, but all contents are
diff --git a/Documentation/git-svn.txt b/Documentation/git-svn.txt
index 636e09048e..d59379ee23 100644
--- a/Documentation/git-svn.txt
+++ b/Documentation/git-svn.txt
@@ -635,7 +635,8 @@ config key: svn.findcopiesharder
-A<filename>::
--authors-file=<filename>::
- Syntax is compatible with the file used by 'git cvsimport':
+ Syntax is compatible with the file used by 'git cvsimport' but
+ an empty email address can be supplied with '<>':
+
------------------------------------------------------------------------
loginname = Joe User <user@example.com>
@@ -654,8 +655,14 @@ config key: svn.authorsfile
If this option is specified, for each SVN committer name that
does not exist in the authors file, the given file is executed
with the committer name as the first argument. The program is
- expected to return a single line of the form "Name <email>",
- which will be treated as if included in the authors file.
+ expected to return a single line of the form "Name <email>" or
+ "Name <>", which will be treated as if included in the authors
+ file.
++
+Due to historical reasons a relative 'filename' is first searched
+relative to the current directory for 'init' and 'clone' and relative
+to the root of the working tree for 'fetch'. If 'filename' is
+not found, it is searched like any other command in '$PATH'.
+
[verse]
config key: svn.authorsProg
diff --git a/Documentation/git-worktree.txt b/Documentation/git-worktree.txt
index e7eb24ab85..2755ca90e3 100644
--- a/Documentation/git-worktree.txt
+++ b/Documentation/git-worktree.txt
@@ -27,11 +27,12 @@ out more than one branch at a time. With `git worktree add` a new working
tree is associated with the repository. This new working tree is called a
"linked working tree" as opposed to the "main working tree" prepared by "git
init" or "git clone". A repository has one main working tree (if it's not a
-bare repository) and zero or more linked working trees.
+bare repository) and zero or more linked working trees. When you are done
+with a linked working tree, remove it with `git worktree remove`.
-When you are done with a linked working tree you can simply delete it.
-The working tree's administrative files in the repository (see
-"DETAILS" below) will eventually be removed automatically (see
+If a working tree is deleted without using `git worktree remove`, then
+its associated administrative files, which reside in the repository
+(see "DETAILS" below), will eventually be removed automatically (see
`gc.worktreePruneExpire` in linkgit:git-config[1]), or you can run
`git worktree prune` in the main or any linked working tree to
clean up any stale administrative files.
@@ -106,7 +107,7 @@ OPTIONS
By default, `add` refuses to create a new working tree when
`<commit-ish>` is a branch name and is already checked out by
another working tree and `remove` refuses to remove an unclean
- working tree. This option overrides that safeguard.
+ working tree. This option overrides these safeguards.
-b <new-branch>::
-B <new-branch>::
@@ -232,7 +233,7 @@ The worktree list command has two output formats. The default format shows the
details on a single line with columns. For example:
------------
-S git worktree list
+$ git worktree list
/path/to/bare-source (bare)
/path/to/linked-worktree abcd1234 [master]
/path/to/other-linked-worktree 1234abc (detached HEAD)
@@ -247,7 +248,7 @@ if the value is true. An empty line indicates the end of a worktree. For
example:
------------
-S git worktree list --porcelain
+$ git worktree list --porcelain
worktree /path/to/bare-source
bare
@@ -278,8 +279,7 @@ $ pushd ../temp
# ... hack hack hack ...
$ git commit -a -m 'emergency fix for boss'
$ popd
-$ rm -rf ../temp
-$ git worktree prune
+$ git worktree remove ../temp
------------
BUGS
diff --git a/Documentation/gitrepository-layout.txt b/Documentation/gitrepository-layout.txt
index c60bcad44a..e85148f05e 100644
--- a/Documentation/gitrepository-layout.txt
+++ b/Documentation/gitrepository-layout.txt
@@ -275,11 +275,6 @@ worktrees/<id>/locked::
or manually by `git worktree prune`. The file may contain a string
explaining why the repository is locked.
-worktrees/<id>/link::
- If this file exists, it is a hard link to the linked .git
- file. It is used to detect if the linked repository is
- manually removed.
-
SEE ALSO
--------
linkgit:git-init[1],
diff --git a/Documentation/howto/recover-corrupted-object-harder.txt b/Documentation/howto/recover-corrupted-object-harder.txt
index 9c4cd0915f..8994e2559e 100644
--- a/Documentation/howto/recover-corrupted-object-harder.txt
+++ b/Documentation/howto/recover-corrupted-object-harder.txt
@@ -80,7 +80,7 @@ valid pack like:
# now add our object data
cat object >>tmp.pack
# and then append the pack trailer
- /path/to/git.git/test-sha1 -b <tmp.pack >trailer
+ /path/to/git.git/t/helper/test-tool sha1 -b <tmp.pack >trailer
cat trailer >>tmp.pack
------------
diff --git a/Documentation/technical/api-directory-listing.txt b/Documentation/technical/api-directory-listing.txt
index 7fae00f44f..4f44ca24f6 100644
--- a/Documentation/technical/api-directory-listing.txt
+++ b/Documentation/technical/api-directory-listing.txt
@@ -53,7 +53,7 @@ The notable options are:
not be returned even if all of its contents are ignored. In
this case, the contents are returned as individual entries.
+
-If this is set, files and directories that explicity match an ignore
+If this is set, files and directories that explicitly match an ignore
pattern are reported. Implicity ignored directories (directories that
do not match an ignore pattern, but whose contents are all ignored)
are not reported, instead all of the contents are reported.
diff --git a/Documentation/technical/api-object-access.txt b/Documentation/technical/api-object-access.txt
index a1162e5bcd..5b29622d00 100644
--- a/Documentation/technical/api-object-access.txt
+++ b/Documentation/technical/api-object-access.txt
@@ -1,7 +1,7 @@
object access API
=================
-Talk about <sha1_file.c> and <object.h> family, things like
+Talk about <sha1-file.c> and <object.h> family, things like
* read_sha1_file()
* read_object_with_reference()
diff --git a/Documentation/technical/hash-function-transition.txt b/Documentation/technical/hash-function-transition.txt
index 417ba491d0..4ab6cd1012 100644
--- a/Documentation/technical/hash-function-transition.txt
+++ b/Documentation/technical/hash-function-transition.txt
@@ -28,11 +28,30 @@ advantages:
address stored content.
Over time some flaws in SHA-1 have been discovered by security
-researchers. https://shattered.io demonstrated a practical SHA-1 hash
-collision. As a result, SHA-1 cannot be considered cryptographically
-secure any more. This impacts the communication of hash values because
-we cannot trust that a given hash value represents the known good
-version of content that the speaker intended.
+researchers. On 23 February 2017 the SHAttered attack
+(https://shattered.io) demonstrated a practical SHA-1 hash collision.
+
+Git v2.13.0 and later subsequently moved to a hardened SHA-1
+implementation by default, which isn't vulnerable to the SHAttered
+attack.
+
+Thus Git has in effect already migrated to a new hash that isn't SHA-1
+and doesn't share its vulnerabilities, its new hash function just
+happens to produce exactly the same output for all known inputs,
+except two PDFs published by the SHAttered researchers, and the new
+implementation (written by those researchers) claims to detect future
+cryptanalytic collision attacks.
+
+Regardless, it's considered prudent to move past any variant of SHA-1
+to a new hash. There's no guarantee that future attacks on SHA-1 won't
+be published in the future, and those attacks may not have viable
+mitigations.
+
+If SHA-1 and its variants were to be truly broken, Git's hash function
+could not be considered cryptographically secure any more. This would
+impact the communication of hash values because we could not trust
+that a given hash value represented the known good version of content
+that the speaker intended.
SHA-1 still possesses the other properties such as fast object lookup
and safe error checking, but other hash functions are equally suitable
@@ -116,10 +135,15 @@ Documentation/technical/repository-version.txt) with extensions
objectFormat = newhash
compatObjectFormat = sha1
-Specifying a repository format extension ensures that versions of Git
-not aware of NewHash do not try to operate on these repositories,
-instead producing an error message:
+The combination of setting `core.repositoryFormatVersion=1` and
+populating `extensions.*` ensures that all versions of Git later than
+`v0.99.9l` will die instead of trying to operate on the NewHash
+repository, instead producing an error message.
+ # Between v0.99.9l and v2.7.0
+ $ git status
+ fatal: Expected git repo version <= 0, found 1
+ # After v2.7.0
$ git status
fatal: unknown repository extensions found:
objectformat