Goal ~~~~ We want to make it possible to use the split-index feature automatically by just setting a new "core.splitIndex" configuration variable to true. This can be valuable as split-index can help significantly speed up `git rebase` especially along with the work to libify `git apply` that has been recently merged to master (see https://github.com/git/git/commit/81358dc238372793b1590efa149cc1581d1fbd98). Design ~~~~~~ The design is similar as the previous work that introduced "core.untrackedCache". The new "core.splitIndex" configuration option can be either true, false or undefined which is the default. When it is true, the split index is created, if it does not already exists, when the index is read. When it is false, the split index is removed if it exists, when the index is read. Otherwise it is left as is. Along with this new configuration variable, the two following options are also introduced: - splitIndex.maxPercentChange This is to avoid having too many changes accumulating in the split index while in split index mode. The git-update-index documentation says: If split-index mode is already enabled and `--split-index` is given again, all changes in $GIT_DIR/index are pushed back to the shared index file. but it is probably better to not expect the user to think about it and to have a mechanism that pushes back all changes to the shared index file automatically when some threshold is reached. The default threshold is when the number of entries in the split index file reaches 20% (by default) of the number of entries in the shared index file. The new "splitIndex.maxPercentChange" config option lets people tweak this value. - splitIndex.sharedIndexExpire To make sure that old sharedindex files are eventually removed when a new one has been created, we "touch" the shared index file every time it is used by a new split index file. Then we can delete shared indexes with an mtime older than one week (by default), when we create a new shared index file. The new "splitIndex.sharedIndexExpire" config option lets people tweak this grace period. This idea was suggested by Duy in: https://public-inbox.org/git/CACsJy8BqMFASHf5kJgUh+bd7XG98CafNydE964VJyPXz-emEvA@xxxxxxxxxxxxxx/ and after some experiments, I agree that it is much simpler than what I thought could be done during our discussion. Highlevel view of the patches in the series ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ Except for patch 1/19, there are 3 big steps, one for each new configuration variable introduced. The main difference between this patch series and the RFC patch series sent last July is that the Step 2 and 3 are new and have been implemented as suggested by Duy. Thanks Duy! - Patch 1/19 is a typo fix in a comment that can be applied separately. Step 1 is: - Patches 2/19 to 5/19 introduce the functions that are reading the "core.splitIndex" configuration variable and tweaking the split index depending on its value. - Patch 6/19 adds a few tests for the new feature. - Patches 7/19 and 8/19 add some documentation for the new feature. Step 2 is: - Patches 9/19 and 10/19 introduce the functions that are reading the "splitIndex.maxPercentChange" configuration variable and regenerating a new shared index file depending on its value. - Patch 11/19 adds a few tests for the new feature. - Patch 12/19 add some documentation for the new feature. Step 3 is: - Patches 13/19 to 16/19 introduce the functions that are reading the "splitIndex.sharedIndexExpire" configuration variable and expiring old shared index files depending on its value. - Patch 17/19 adds a few tests for the new feature. - Patches 18/19 and 19/19 add some documentation for the new feature. Links ~~~~~ This patch series is also available here: https://github.com/chriscool/git/commits/config-split-index The previous RFC version was: https://github.com/chriscool/git/commits/config-split-index7 On the mailing list the related patch series and discussions were: https://public-inbox.org/git/20160711172254.13439-1-chriscool@xxxxxxxxxxxxx/ Christian Couder (19): split-index: s/eith/with/ typo fix config: add git_config_get_split_index() split-index: add {add,remove}_split_index() functions read-cache: add and then use tweak_split_index() update-index: warn in case of split-index incoherency t1700: add tests for core.splitIndex Documentation/config: add information for core.splitIndex Documentation/git-update-index: talk about core.splitIndex config var config: add git_config_get_max_percent_split_change() read-cache: regenerate shared index if necessary t1700: add tests for splitIndex.maxPercentChange Documentation/config: add splitIndex.maxPercentChange sha1_file: make check_and_freshen_file() non static read-cache: touch shared index files when used config: add git_config_get_date_string() from gc.c read-cache: unlink old sharedindex files t1700: test shared index file expiration Documentation/config: add splitIndex.sharedIndexExpire Documentation/git-update-index: explain splitIndex.* Documentation/config.txt | 28 +++++++ Documentation/git-update-index.txt | 39 ++++++++-- builtin/gc.c | 15 +--- builtin/update-index.c | 25 +++--- cache.h | 6 ++ config.c | 39 ++++++++++ read-cache.c | 119 +++++++++++++++++++++++++++- sha1_file.c | 2 +- split-index.c | 24 +++++- split-index.h | 2 + t/t1700-split-index.sh | 154 +++++++++++++++++++++++++++++++++++++ 11 files changed, 417 insertions(+), 36 deletions(-) -- 2.10.1.462.g7e1e03a