[PATCH v5] status: long status advice adapted to recent capabilities

From: Rudy Rigot <rudy.rigot@gmail.com>

Improve the advice displayed when `git status` is slow because of excessive numbers of untracked files. Update the `git status` man page to explain the various configuration options.

`git status` can be slow when there are a large number of untracked files and directories, because Git must search the entire worktree to enumerate them. Previously, Git would print an advice message with the elapsed search time and a suggestion to disable the search using the `-uno` option. This suggestion also carried a warning that might scare off some users.

Git can reduce the size and time of the untracked file search when the `core.untrackedCache` and `core.fsmonitor` features are enabled by caching results from previous `git status` invocations.

Update the advice to explain the various combinations of additional configuration options and refer to (new) documentation in the man page that explains it in more detail than what can be printed in an advice message.

Finally, add new tests to verify the new functionality.

Signed-off-by: Rudy Rigot <rudy.rigot@gmail.com>
---
    status: long status advice adapted to recent capabilities
    
    Here is version 5 for this patch.
    
    Changes since v4:
    
     * Test improvements (readability, isolation. ...)
     * Doc improvements (referencing other docs, adding advice to try again,
       ...)
     * Minor logic simplifications

Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-1384%2Frudyrigot%2Fadvice_statusFsmonitor-v5
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-1384/rudyrigot/advice_statusFsmonitor-v5
Pull-Request: https://github.com/gitgitgadget/git/pull/1384

Range-diff vs v4:

 1:  85b35882c02 ! 1:  8b1b9ee094f status: long status advice adapted to recent capabilities
     @@ Documentation/git-status.txt: during the write may conflict with other simultane
      +--------------------------------
      +
      +`git status` can be very slow in large worktrees if/when it
     -+needs to search for untracked files and directories.  There are
     ++needs to search for untracked files and directories. There are
      +many configuration options available to speed this up by either
      +avoiding the work or making use of cached results from previous
     -+Git commands.  Since we all work in different ways, there is no
     -+single optimum set of settings right for everyone.  Here is a
     -+brief summary of the relevant options to help you choose which
     -+is right for you.  Each of these settings is independently
     -+documented elsewhere in more detail, so please refer to them
     -+for complete details.
     -+
     -+* The `-uno` flag or the `status.showUntrackedfiles=false`
     -+    config : indicate that `git status` should not report untracked
     ++Git commands. There is no single optimum set of settings right
     ++for everyone.  Here is a brief summary of the relevant options
     ++to help you choose which is right for you.
     ++
     ++* First, you may want to run `git status` again. Your current
     ++	configuration may already be caching `git status` results,
     ++	so it could be faster on subsequent runs.
     ++
     ++* The `--untracked-files=no` flag or the
     ++	`status.showUntrackedfiles=false` config (see above for both) :
     ++	indicate that `git status` should not report untracked
      +	files. This is the fastest option. `git status` will not list
      +	the untracked files, so you need to be careful to remember if
      +	you create any new files and manually `git add` them.
      +
     -+* `advice.statusUoption=false` : this config option disables a
     -+	warning message when the search for untracked files takes longer
     -+	than desired. In some large repositories, this message may appear
     -+	frequently and not be a helpful signal.
     -+
     -+* `core.untrackedCache=true` : enable the untracked cache feature
     -+    and only search directories that have been modified since the
     -+    previous `git status` command.  Git remembers the set of
     -+    untracked files within each directory and assumes that if a
     -+    directory has not been modified, then the set of untracked
     -+    file within has not changed.  This is much faster than
     -+    enumerating the contents of every directory, but still not
     -+    without cost, because Git still has to search for the set of
     -+    modified directories. The untracked cache is stored in the
     ++* `advice.statusUoption=false` (see linkgit:git-config[1]) :
     ++	this config option disables a warning message when the search
     ++	for untracked files takes longer than desired. In some large
     ++	repositories, this message may appear frequently and not be a
     ++	helpful signal.
     ++
     ++* `core.untrackedCache=true` (see linkgit:git-update-index[1]) :
     ++	enable the untracked cache feature and only search directories
     ++	that have been modified since the previous `git status` command.
     ++	Git remembers the set of untracked files within each directory
     ++	and assumes that if a directory has not been modified, then
     ++	the set of untracked file within has not changed.  This is much
     ++	faster than enumerating the contents of every directory, but still
     ++	not without cost, because Git still has to search for the set of
     ++	modified directories. The untracked cache is stored in the
      +	.git/index file. The reduced cost searching for untracked
      +	files is offset slightly by the increased size of the index and
      +	the cost of keeping it up-to-date. That reduced search time is
      +	usually worth the additional size.
      +
      +* `core.untrackedCache=true` and `core.fsmonitor=true` or
     -+    `core.fsmonitor=<hook_command_pathname>` : enable both the
     -+    untracked cache and FSMonitor features and only search
     -+    directories that have been modified since the previous
     -+    `git status` command.  This is faster than using just the
     -+    untracked cache alone because Git can also avoid searching
     -+    for modified directories.  Git only has to enumerate the
     -+    exact set of directories that have changed recently. While
     -+	the FSMonitor feature can be enabled without the untracked
     -+	cache, the benefits are greatly reduced in that case.
     ++	`core.fsmonitor=<hook_command_pathname>` (see
     ++	linkgit:git-update-index[1]) : enable both the untracked cache
     ++	and FSMonitor features and only search directories that have
     ++	been modified since the previous `git status` command.  This
     ++	is faster than using just the untracked cache alone because
     ++	Git can also avoid searching for modified directories.  Git
     ++	only has to enumerate the exact set of directories that have
     ++	changed recently. While the FSMonitor feature can be enabled
     ++	without the untracked cache, the benefits are greatly reduced
     ++	in that case.
      +
      +Note that after you turn on the untracked cache and/or FSMonitor
      +features it may take a few `git status` commands for the various
     @@ t/t7065-wtstatus-slow.sh (new)
      +
      +. ./test-lib.sh
      +
     -+DATA="$TEST_DIRECTORY/t7065"
     -+
      +GIT_TEST_UF_DELAY_WARNING=1
      +export GIT_TEST_UF_DELAY_WARNING
      +
      +test_expect_success setup '
     -+	git checkout -b test
     ++	git checkout -b test &&
     ++	echo "actual" >> .gitignore &&
     ++	echo "expected" >> .gitignore &&
     ++	echo "out" >> .gitignore &&
     ++	git add .gitignore &&
     ++	git commit -m "Add .gitignore"
      +'
      +
      +test_expect_success 'when core.untrackedCache and fsmonitor are unset' '
     -+	test_must_fail git config --get core.untrackedCache &&
     -+	test_must_fail git config --get core.fsmonitor &&
     -+	git status | sed "s/[0-9]\.[0-9][0-9]/X/g" >../actual &&
     -+	cat >../expected <<-EOF &&
     -+On branch test
     -+
     -+No commits yet
     -+
     ++	test_might_fail git config --unset-all core.untrackedCache &&
     ++	test_might_fail git config --unset-all core.fsmonitor &&
     ++	git status >out &&
     ++	sed "s/[0-9]\.[0-9][0-9]/X/g" out >actual &&
     ++	cat >expected <<-\EOF &&
     ++		On branch test
      +
     -+It took X seconds to enumerate untracked files.
     -+See '"'"'git help status'"'"' for information on how to improve this.
     ++		It took X seconds to enumerate untracked files.
     ++		See '"'"'git help status'"'"' for information on how to improve this.
      +
     -+nothing to commit (create/copy files and use "git add" to track)
     ++		nothing to commit, working tree clean
      +	EOF
     -+	test_cmp ../expected ../actual &&
     -+	rm -fr ../actual ../expected
     ++	test_cmp expected actual
      +'
      +
      +test_expect_success 'when core.untrackedCache true, but not fsmonitor' '
      +	git config core.untrackedCache true &&
     -+	test_must_fail git config --get core.fsmonitor &&
     -+	git status | sed "s/[0-9]\.[0-9][0-9]/X/g" >../actual &&
     -+	cat >../expected <<-EOF &&
     -+On branch test
     ++	test_might_fail git config --unset-all core.fsmonitor &&
     ++	git status >out &&
     ++	sed "s/[0-9]\.[0-9][0-9]/X/g" out >actual &&
     ++	cat >expected <<-\EOF &&
     ++		On branch test
      +
     -+No commits yet
     ++		It took X seconds to enumerate untracked files.
     ++		See '"'"'git help status'"'"' for information on how to improve this.
      +
     -+
     -+It took X seconds to enumerate untracked files.
     -+See '"'"'git help status'"'"' for information on how to improve this.
     -+
     -+nothing to commit (create/copy files and use "git add" to track)
     ++		nothing to commit, working tree clean
      +	EOF
     -+	test_cmp ../expected ../actual &&
     -+	rm -fr ../actual ../expected
     ++	test_cmp expected actual
      +'
      +
      +test_expect_success 'when core.untrackedCache true, and fsmonitor' '
      +	git config core.untrackedCache true &&
      +	git config core.fsmonitor true &&
     -+	git status | sed "s/[0-9]\.[0-9][0-9]/X/g" >../actual &&
     -+	cat >../expected <<-EOF &&
     -+On branch test
     -+
     -+No commits yet
     -+
     ++	git status >out &&
     ++	sed "s/[0-9]\.[0-9][0-9]/X/g" out >actual &&
     ++	cat >expected <<-\EOF &&
     ++		On branch test
      +
     -+It took X seconds to enumerate untracked files,
     -+but this is currently being cached.
     -+See '"'"'git help status'"'"' for information on how to improve this.
     ++		It took X seconds to enumerate untracked files,
     ++		but this is currently being cached.
     ++		See '"'"'git help status'"'"' for information on how to improve this.
      +
     -+nothing to commit (create/copy files and use "git add" to track)
     ++		nothing to commit, working tree clean
      +	EOF
     -+	test_cmp ../expected ../actual &&
     -+	rm -fr ../actual ../expected
     ++	test_cmp expected actual
      +'
      +
      +test_done
     @@ wt-status.c: static void wt_longstatus_print_tracking(struct wt_status *s)
       
      +static inline int uf_was_slow(uint32_t untracked_in_ms)
      +{
     -+	const char *x;
     -+	x = getenv("GIT_TEST_UF_DELAY_WARNING");
     -+	if (x) {
     ++	if (getenv("GIT_TEST_UF_DELAY_WARNING")) {
      +		untracked_in_ms += UF_DELAY_WARNING_IN_MS + 1;
      +	}
      +

 Documentation/git-status.txt | 59 +++++++++++++++++++++++++++++++
 t/t7065-wtstatus-slow.sh     | 68 ++++++++++++++++++++++++++++++++++++
 wt-status.c                  | 30 +++++++++++++---
 3 files changed, 152 insertions(+), 5 deletions(-)
 create mode 100755 t/t7065-wtstatus-slow.sh