Default to substring filtering, add option to go back to fuzzy filtering

By default we now search for substrings; you can search for multiple substrings
by separating them with spaces. Add a config option gui.filterMode that can be
set to 'fuzzy' to switch back to the previous behavior.

12 files changed, 164 insertions, 52 deletions

diff --git a/docs/Config.md b/docs/Config.md
index 6998b2296..4e2486784 100644
--- a/docs/Config.md
+++ b/docs/Config.md
@@ -86,6 +86,7 @@ gui:
   border: 'rounded' # one of 'single' | 'double' | 'rounded' | 'hidden'
   animateExplosion: true # shows an explosion animation when nuking the working tree
   portraitMode: 'auto' # one of 'auto' | 'never' | 'always'
+  filterMode: 'substring' # one of 'substring' | 'fuzzy'; see 'Filtering' section below
 git:
   paging:
     colorArg: always
@@ -374,6 +375,12 @@ That's the behavior when `gui.scrollOffBehavior` is set to "margin" (the default
 
 This setting applies both to all list views (e.g. commits and branches etc), and to the staging view.
 
+## Filtering
+
+We have two ways to filter things, substring matching (the default) and fuzzy searching. With substring matching, the text you enter gets searched for verbatim (usually case-insensitive, except when your filter string contains uppercase letters, in which case we search case-sensitively). You can search for multiple non-contiguous substrings by separating them with spaces; for example, "int test" will match "integration-testing". All substrings have to match, but not necessarily in the given order.
+
+Fuzzy searching is smarter in that it allows every letter of the filter string to match anywhere in the text (only in order though), assigning a weight to the quality of the match and sorting by that order. This has the advantage that it allows typing "clt" to match "commit_loader_test" (letters at the beginning of subwords get more weight); but it has the disadvantage that it tends to return lots of irrelevant results, especially with short filter strings.
+
 ## Color Attributes
 
 For color attributes you can choose an array of attributes (with max one color attribute)
diff --git a/pkg/config/user_config.go b/pkg/config/user_config.go
index 2cbb15ce4..588fe2638 100644
--- a/pkg/config/user_config.go
+++ b/pkg/config/user_config.go
@@ -142,6 +142,13 @@ type GuiConfig struct {
 	// Whether to stack UI components on top of each other.
 	// One of 'auto' (default) | 'always' | 'never'
 	PortraitMode string `yaml:"portraitMode"`
+	// How things are filtered when typing '/'.
+	// One of 'substring' (default) | 'fuzzy'
+	FilterMode string `yaml:"filterMode" jsonschema:"enum=substring,enum=fuzzy"`
+}
+
+func (c *GuiConfig) UseFuzzySearch() bool {
+	return c.FilterMode == "fuzzy"
 }
 
 type ThemeConfig struct {
@@ -660,6 +667,7 @@ func GetDefaultConfig() *UserConfig {
 			Border:                    "rounded",
 			AnimateExplosion:          true,
 			PortraitMode:              "auto",
+			FilterMode:                "substring",
 		},
 		Git: GitConfig{
 			Paging: PagingConfig{
diff --git a/pkg/gui/context/filtered_list.go b/pkg/gui/context/filtered_list.go
index 13b9c166a..8ac912cd0 100644
--- a/pkg/gui/context/filtered_list.go
+++ b/pkg/gui/context/filtered_list.go
@@ -39,18 +39,18 @@ func (self *FilteredList[T]) GetFilter() string {
 	return self.filter
 }
 
-func (self *FilteredList[T]) SetFilter(filter string) {
+func (self *FilteredList[T]) SetFilter(filter string, useFuzzySearch bool) {
 	self.filter = filter
 
-	self.applyFilter()
+	self.applyFilter(useFuzzySearch)
 }
 
 func (self *FilteredList[T]) ClearFilter() {
-	self.SetFilter("")
+	self.SetFilter("", false)
 }
 
-func (self *FilteredList[T]) ReApplyFilter() {
-	self.applyFilter()
+func (self *FilteredList[T]) ReApplyFilter(useFuzzySearch bool) {
+	self.applyFilter(useFuzzySearch)
 }
 
 func (self *FilteredList[T]) IsFiltering() bool {
@@ -84,7 +84,7 @@ func (self *fuzzySource[T]) Len() int {
 	return len(self.list)
 }
 
-func (self *FilteredList[T]) applyFilter() {
+func (self *FilteredList[T]) applyFilter(useFuzzySearch bool) {
 	self.mutex.Lock()
 	defer self.mutex.Unlock()
 
@@ -96,11 +96,11 @@ func (self *FilteredList[T]) applyFilter() {
 			getFilterFields: self.getFilterFields,
 		}
 
-		matches := fuzzy.FindFrom(self.filter, source)
+		matches := utils.FindFrom(self.filter, source, useFuzzySearch)
 		self.filteredIndices = lo.Map(matches, func(match fuzzy.Match, _ int) int {
 			return match.Index
 		})
-		if self.shouldRetainSortOrder != nil && self.shouldRetainSortOrder() {
+		if useFuzzySearch && self.shouldRetainSortOrder != nil && self.shouldRetainSortOrder() {
 			slices.Sort(self.filteredIndices)
 		}
 	}
diff --git a/pkg/gui/controllers/custom_command_action.go b/pkg/gui/controllers/custom_command_action.go
index bc595934d..16d811aff 100644
--- a/pkg/gui/controllers/custom_command_action.go
+++ b/pkg/gui/controllers/custom_command_action.go
@@ -38,7 +38,7 @@ func (self *CustomCommandAction) Call() error {
 func (self *CustomCommandAction) GetCustomCommandsHistorySuggestionsFunc() func(string) []*types.Suggestion {
 	history := self.c.GetAppState().CustomCommandsHistory
 
-	return helpers.FuzzySearchFunc(history)
+	return helpers.FuzzySearchFunc(history, self.c.UserConfig.Gui.UseFuzzySearch())
 }
 
 // this mimics the shell functionality `ignorespace`
diff --git a/pkg/gui/controllers/helpers/search_helper.go b/pkg/gui/controllers/helpers/search_helper.go
index 9ceea2f90..c31720949 100644
--- a/pkg/gui/controllers/helpers/search_helper.go
+++ b/pkg/gui/controllers/helpers/search_helper.go
@@ -218,7 +218,7 @@ func (self *SearchHelper) OnPromptContentChanged(searchString string) {
 	case types.IFilterableContext:
 		context.SetSelection(0)
 		_ = context.GetView().SetOriginY(0)
-		context.SetFilter(searchString)
+		context.SetFilter(searchString, self.c.UserConfig.Gui.UseFuzzySearch())
 		_ = self.c.PostRefreshUpdate(context)
 	case types.ISearchableContext:
 		// do nothing
@@ -234,7 +234,7 @@ func (self *SearchHelper) ReApplyFilter(context types.Context) {
 		if ok {
 			filterableContext.SetSelection(0)
 			_ = filterableContext.GetView().SetOriginY(0)
-			filterableContext.ReApplyFilter()
+			filterableContext.ReApplyFilter(self.c.UserConfig.Gui.UseFuzzySearch())
 		}
 	}
 }
diff --git a/pkg/gui/controllers/helpers/suggestions_helper.go b/pkg/gui/controllers/helpers/suggestions_helper.go
index 2ae9d2158..91f42df8c 100644
--- a/pkg/gui/controllers/helpers/suggestions_helper.go
+++ b/pkg/gui/controllers/helpers/suggestions_helper.go
@@ -3,6 +3,7 @@ package helpers
 import (
 	"fmt"
 	"os"
+	"strings"
 
 	"github.com/jesseduffield/gocui"
 	"github.com/jesseduffield/lazygit/pkg/commands/models"
@@ -65,7 +66,7 @@ func matchesToSuggestions(matches []string) []*types.Suggestion {
 func (self *SuggestionsHelper) GetRemoteSuggestionsFunc() func(string) []*types.Suggestion {
 	remoteNames := self.getRemoteNames()
 
-	return FuzzySearchFunc(remoteNames)
+	return FuzzySearchFunc(remoteNames, self.c.UserConfig.Gui.UseFuzzySearch())
 }
 
 func (self *SuggestionsHelper) getBranchNames() []string {
@@ -82,7 +83,7 @@ func (self *SuggestionsHelper) GetBranchNameSuggestionsFunc() func(string) []*ty
 		if input == "" {
 			matchingBranchNames = branchNames
 		} else {
-			matchingBranchNames = utils.FuzzySearch(input, branchNames)
+			matchingBranchNames = utils.FuzzySearch(input, branchNames, self.c.UserConfig.Gui.UseFuzzySearch())
 		}
 
 		return lo.Map(matchingBranchNames, func(branchName string, _ int) *types.Suggestion {
@@ -128,13 +129,26 @@ func (self *SuggestionsHelper) GetFilePathSuggestionsFunc() func(string) []*type
 
 	return func(input string) []*types.Suggestion {
 		matchingNames := []string{}
-		_ = self.c.Model().FilesTrie.VisitFuzzy(patricia.Prefix(input), true, func(prefix patricia.Prefix, item patricia.Item, skipped int) error {
-			matchingNames = append(matchingNames, item.(string))
-			return nil
-		})
+		if self.c.UserConfig.Gui.UseFuzzySearch() {
+			_ = self.c.Model().FilesTrie.VisitFuzzy(patricia.Prefix(input), true, func(prefix patricia.Prefix, item patricia.Item, skipped int) error {
+				matchingNames = append(matchingNames, item.(string))
+				return nil
+			})
 
-		// doing another fuzzy search for good measure
-		matchingNames = utils.FuzzySearch(input, matchingNames)
+			// doing another fuzzy search for good measure
+			matchingNames = utils.FuzzySearch(input, matchingNames, true)
+		} else {
+			substrings := strings.Fields(input)
+			_ = self.c.Model().FilesTrie.Visit(func(prefix patricia.Prefix, item patricia.Item) error {
+				for _, sub := range substrings {
+					if !utils.CaseAwareContains(item.(string), sub) {
+						return nil
+					}
+				}
+				matchingNames = append(matchingNames, item.(string))
+				return nil
+			})
+		}
 
 		return matchesToSuggestions(matchingNames)
 	}
@@ -149,7 +163,7 @@ func (self *SuggestionsHelper) getRemoteBranchNames(separator string) []string {
 }
 
 func (self *SuggestionsHelper) GetRemoteBranchesSuggestionsFunc(separator string) func(string) []*types.Suggestion {
-	return FuzzySearchFunc(self.getRemoteBranchNames(separator))
+	return FuzzySearchFunc(self.getRemoteBranchNames(separator), self.c.UserConfig.Gui.UseFuzzySearch())
 }
 
 func (self *SuggestionsHelper) getTagNames() []string {
@@ -161,7 +175,7 @@ func (self *SuggestionsHelper) getTagNames() []string {
 func (self *SuggestionsHelper) GetTagsSuggestionsFunc() func(string) []*types.Suggestion {
 	tagNames := self.getTagNames()
 
-	return FuzzySearchFunc(tagNames)
+	return FuzzySearchFunc(tagNames, self.c.UserConfig.Gui.UseFuzzySearch())
 }
 
 func (self *SuggestionsHelper) GetRefsSuggestionsFunc() func(string) []*types.Suggestion {
@@ -172,7 +186,7 @@ func (self *SuggestionsHelper) GetRefsSuggestionsFunc() func(string) []*types.Su
 
 	refNames := append(append(append(remoteBranchNames, localBranchNames...), tagNames...), additionalRefNames...)
 
-	return FuzzySearchFunc(refNames)
+	return FuzzySearchFunc(refNames, self.c.UserConfig.Gui.UseFuzzySearch())
 }
 
 func (self *SuggestionsHelper) GetAuthorsSuggestionsFunc() func(string) []*types.Suggestion {
@@ -182,16 +196,16 @@ func (self *SuggestionsHelper) GetAuthorsSuggestionsFunc() func(string) []*types
 
 	slices.Sort(authors)
 
-	return FuzzySearchFunc(authors)
+	return FuzzySearchFunc(authors, self.c.UserConfig.Gui.UseFuzzySearch())
 }
 
-func FuzzySearchFunc(options []string) func(string) []*types.Suggestion {
+func FuzzySearchFunc(options []string, useFuzzySearch bool) func(string) []*types.Suggestion {
 	return func(input string) []*types.Suggestion {
 		var matches []string
 		if input == "" {
 			matches = options
 		} else {
-			matches = utils.FuzzySearch(input, options)
+			matches = utils.FuzzySearch(input, options, useFuzzySearch)
 		}
 
 		return matchesToSuggestions(matches)
diff --git a/pkg/gui/types/context.go b/pkg/gui/types/context.go
index 92b07a729..bb57375f9 100644
--- a/pkg/gui/types/context.go
+++ b/pkg/gui/types/context.go
@@ -102,10 +102,10 @@ type IFilterableContext interface {
 	IListPanelState
 	ISearchHistoryContext
 
-	SetFilter(string)
+	SetFilter(string, bool)
 	GetFilter() string
 	ClearFilter()
-	ReApplyFilter()
+	ReApplyFilter(bool)
 	IsFiltering() bool
 	IsFilterableContext()
 }
diff --git a/pkg/i18n/english.go b/pkg/i18n/english.go
index f475ec756..29b78f601 100644
--- a/pkg/i18n/english.go
+++ b/pkg/i18n/english.go
@@ -1906,6 +1906,10 @@ keybinding:
 - Push/pull/fetch loading statuses are now shown against the branch rather than in a popup. This allows you to e.g. fetch multiple branches in parallel and see the status for each branch.
 - The git log graph in the commits view is now always shown by default (previously it was only shown when the view was maximised). If you find this too noisy, you can change it back via ctrl+L -> 'Show git graph' -> 'when maximised'
 - Pressing space on a remote branch used to show a prompt for entering a name for a new local branch to check out from the remote branch. Now it just checks out the remote branch directly, letting you choose between a new local branch with the same name, or a detached head. The old behavior is still available via the 'n' keybinding.
+- Filtering (e.g. when pressing '/') is less fuzzy by default; it only matches substrings now. Multiple substrings can be matched by separating them with spaces. If you want to revert to the old behavior, set the following in your config:
+
+gui:
+  filterMode: 'fuzzy'
 	  `,
 		},
 	}
diff --git a/pkg/integration/tests/filter_and_search/filter_fuzzy.go b/pkg/integration/tests/filter_and_search/filter_fuzzy.go
index 198020afa..63df903d8 100644
--- a/pkg/integration/tests/filter_and_search/filter_fuzzy.go
+++ b/pkg/integration/tests/filter_and_search/filter_fuzzy.go
@@ -9,7 +9,9 @@ var FilterFuzzy = NewIntegrationTest(NewIntegrationTestArgs{
 	Description:  "Verify that fuzzy filtering works (not just exact matches)",
 	ExtraCmdArgs: []string{},
 	Skip:         false,
-	SetupConfig:  func(config *config.AppConfig) {},
+	SetupConfig: func(config *config.AppConfig) {
+		config.UserConfig.Gui.FilterMode = "fuzzy"
+	},
 	SetupRepo: func(shell *Shell) {
 		shell.NewBranch("this-is-my-branch")
 		shell.EmptyCommit("first commit")
diff --git a/pkg/utils/search.go b/pkg/utils/search.go
index ab780c5dd..7abe8c85d 100644
--- a/pkg/utils/search.go
+++ b/pkg/utils/search.go
@@ -7,18 +7,67 @@ import (
 	"github.com/samber/lo"
 )
 
-func FuzzySearch(needle string, haystack []string) []string {
+func FuzzySearch(needle string, haystack []string, useFuzzySearch bool) []string {
 	if needle == "" {
 		return []string{}
 	}
 
-	matches := fuzzy.Find(needle, haystack)
+	matches := Find(needle, haystack, useFuzzySearch)
 
 	return lo.Map(matches, func(match fuzzy.Match, _ int) string {
 		return match.Str
 	})
 }
 
+// Duplicated from the fuzzy package because it's private there
+type stringSource []string
+
+func (ss stringSource) String(i int) string {
+	return ss[i]
+}
+
+func (ss stringSource) Len() int { return len(ss) }
+
+// Drop-in replacement for fuzzy.Find (except that it doesn't fill out
+// MatchedIndexes or Score, but we are not using these)
+func FindSubstrings(pattern string, data []string) fuzzy.Matches {
+	return FindSubstringsFrom(pattern, stringSource(data))
+}
+
+// Drop-in replacement for fuzzy.FindFrom (except that it doesn't fill out
+// MatchedIndexes or Score, but we are not using these)
+func FindSubstringsFrom(pattern string, data fuzzy.Source) fuzzy.Matches {
+	substrings := strings.Fields(pattern)
+	result := fuzzy.Matches{}
+
+outer:
+	for i := 0; i < data.Len(); i++ {
+		s := data.String(i)
+		for _, sub := range substrings {
+			if !CaseAwareContains(s, sub) {
+				continue outer
+			}
+		}
+		result = append(result, fuzzy.Match{Str: s, Index: i})
+	}
+
+	return result
+}
+
+func Find(pattern string, data []string, useFuzzySearch bool) fuzzy.Matches {
+	if useFuzzySearch {
+		return fuzzy.Find(pattern, data)
+	}
+	return FindSubstrings(pattern, data)
+}
+
+func FindFrom(pattern string, data fuzzy.Source, useFuzzySearch bool) fuzzy.Matches {
+	if useFuzzySearch {
+		return fuzzy.FindFrom(pattern, data)
+	}
+	return FindSubstringsFrom(pattern, data)
+}
+
 func CaseAwareContains(haystack, needle string) bool {
 	// if needle contains an uppercase letter, we'll do a case sensitive search
 	if ContainsUppercase(needle) {
diff --git a/pkg/utils/search_test.go b/pkg/utils/search_test.go
index 79668c0f5..fef10ed59 100644
--- a/pkg/utils/search_test.go
+++ b/pkg/utils/search_test.go
@@ -10,46 +10,65 @@ import (
 // TestFuzzySearch is a function.
 func TestFuzzySearch(t *testing.T) {
 	type scenario struct {
-		needle   string
-		haystack []string
-		expected []string
+		needle         string
+		haystack       []string
+		useFuzzySearch bool
+		expected       []string
 	}
 
 	scenarios := []scenario{
 		{
-			needle:   "",
-			haystack: []string{"test"},
-			expected: []string{},
+			needle:         "",
+			haystack:       []string{"test"},
+			useFuzzySearch: true,
+			expected:       []string{},
+		},
+		{
+			needle:         "test",
+			haystack:       []string{"test"},
+			useFuzzySearch: true,
+			expected:       []string{"test"},
+		},
+		{
+			needle:         "o",
+			haystack:       []string{"a", "o", "e"},
+			useFuzzySearch: true,
+			expected:       []string{"o"},
 		},
 		{
-			needle:   "test",
-			haystack: []string{"test"},
-			expected: []string{"test"},
+			needle:         "mybranch",
+			haystack:       []string{"my_branch", "mybranch", "branch", "this is my branch"},
+			useFuzzySearch: true,
+			expected:       []string{"mybranch", "my_branch", "this is my branch"},
 		},
 		{
-			needle:   "o",
-			haystack: []string{"a", "o", "e"},
-			expected: []string{"o"},
+			needle:         "test",
+			haystack:       []string{"not a good match", "this 'test' is a good match", "test"},
+			useFuzzySearch: true,
+			expected:       []string{"test", "this 'test' is a good match"},
 		},
 		{
-			needle:   "mybranch",
-			haystack: []string{"my_branch", "mybranch", "branch", "this is my branch"},
-			expected: []string{"mybranch", "my_branch", "this is my branch"},
+			needle:         "test",
+			haystack:       []string{"Test"},
+			useFuzzySearch: true,
+			expected:       []string{"Test"},
 		},
 		{
-			needle:   "test",
-			haystack: []string{"not a good match", "this 'test' is a good match", "test"},
-			expected: []string{"test", "this 'test' is a good match"},
+			needle:         "test",
+			haystack:       []string{"integration-testing", "t_e_s_t"},
+			useFuzzySearch: false,
+			expected:       []string{"integration-testing"},
 		},
 		{
-			needle:   "test",
-			haystack: []string{"Test"},
-			expected: []string{"Test"},
+			needle:         "integr test",
+			haystack:       []string{"integration-testing", "testing-integration"},
+			useFuzzySearch: false,
+			expected:       []string{"integration-testing", "testing-integration"},
 		},
 	}
 
 	for _, s := range scenarios {
-		assert.EqualValues(t, s.expected, FuzzySearch(s.needle, s.haystack))
+		assert.EqualValues(t, s.expected, FuzzySearch(s.needle, s.haystack, s.useFuzzySearch))
 	}
 }
 
diff --git a/schema/config.json b/schema/config.json
index 3816dcea6..65383cd9f 100644
--- a/schema/config.json
+++ b/schema/config.json
@@ -357,6 +357,15 @@
           "type": "string",
           "description": "Whether to stack UI components on top of each other.\nOne of 'auto' (default) | 'always' | 'never'",
           "default": "auto"
+        },
+        "filterMode": {
+          "type": "string",
+          "enum": [
+            "substring",
+            "fuzzy"
+          ],
+          "description": "How things are filtered when typing '/'.\nOne of 'substring' (default) | 'fuzzy'",
+          "default": "substring"
         }
       },
       "additionalProperties": false,