Merge branch 'stable-5.13' into stable-6.0

* stable-5.13:
  Add pack options to preserve and prune old pack files
  Allow to perform PackedBatchRefUpdate without locking loose refs
  Document option "core.sha1Implementation" introduced in 59029aec

Change-Id: I423f410578f5bbe178832b80fef8998a5372182c

1 files changed, 3 insertions, 2 deletions

diff --git a/Documentation/config-options.md b/Documentation/config-options.md
index b4a0c1d98c..5d76483acf 100644
--- a/Documentation/config-options.md
+++ b/Documentation/config-options.md
@@ -42,6 +42,7 @@ For details on native git options see also the official [git config documentatio
 | `core.precomposeUnicode` | `true` on Mac OS | ✅ | MacOS only. When `true`, JGit reverts the unicode decomposition of filenames done by Mac OS. |
 | `core.quotePath` | `true` | ✅ | Commands that output paths (e.g. ls-files, diff), will quote "unusual" characters in the pathname by enclosing the pathname in double-quotes and escaping those characters with backslashes in the same way C escapes control characters (e.g. `\t` for TAB, `\n` for LF, `\\` for backslash) or bytes with values larger than `0x80` (e.g. octal `\302\265` for "micro" in UTF-8). |
 | `core.repositoryFormatVersion` | `1` | ⃞ | Internal version identifying the repository format and layout version. Don't set manually. |
+| `core.sha1Implementation` | `java` | ⃞ | Choose the SHA1 implementation used by JGit. Set it to `java` to use JGit's Java implementation which detects SHA1 collisions if system property `org.eclipse.jgit.util.sha1.detectCollision` is unset or `true`. Set it to `jdkNative` to use the native implementation available in the JDK, can also be set using system property `org.eclipse.jgit.util.sha1.implementation`. If both are set the system property takes precedence. Performance of `jdkNative` is around 10% higher than `java` when `detectCollision=false` and 30% higher when `detectCollision=true`.|
 | `core.streamFileThreshold` | `50 MiB` | ⃞ | The size threshold beyond which objects must be streamed. |
 | `core.supportsAtomicFileCreation` | `true` | ⃞ | Whether the filesystem supports atomic file creation. |
 | `core.symlinks` | Auto detect if filesystem supports symlinks| ✅ | If false, symbolic links are checked out as small plain files that contain the link text. |
@@ -99,8 +100,8 @@ Proxy configuration uses the standard Java mechanisms via class `java.net.ProxyS
 | `pack.depth` | `50` | ✅ | Maximum depth of delta chain set up for the pack writer. |
 | `pack.indexVersion` | `2` | ✅ | Pack index file format version. |
 | `pack.minSizePreventRacyPack` | `100 MiB` | ⃞ | Minimum packfile size for which we wait before opening a newly written pack to prevent its lastModified timestamp could be racy if `pack.waitPreventRacyPack` is `true`. |
-| `pack.preserveOldPacks` | `false` | ⃞ | Whether to preserve old packs in a preserved directory. |
-| `prunePreserved`, only via API of PackConfig | `false` | ⃞ | Whether to remove preserved pack files in a preserved directory. |
+| `pack.preserveOldPacks` | `false` | ⃞ | Whether to preserve old packs during gc in the `objects/pack/preserved` directory. This can avoid rare races between gc removing pack files and other concurrent operations. If this option is false data loss can occur in rare cases when an object is believed to be unreferenced when object repacking is running, and then garbage collection deletes it while another concurrent operation references this object shortly before garbage collection deletes it. When this happens, a new reference is created which points to a now missing object. |
+| `pack.prunePreserved` | `false` | ⃞ | Whether to prune preserved pack files from the previous run of gc from the `objects/pack/preserved` directory. This helps to limit the additional storage space needed to preserve old packs when `pack.preserveOldPacks = true`. |
 | `pack.reuseDeltas` | `true` |⃞ | Whether to reuse deltas existing in repository. |
 | `pack.reuseObjects` | `true` | ⃞ | Whether to reuse existing objects representation in repository. |
 | `pack.searchForReuseTimeout` | | ⃞ | Search for reuse phase timeout. Expressed as a `Duration`, i.e.: `50sec`. |