How the Log Works

The Log is the commit history of the active repository, drawn as a branch graph with the details of the selected commit below it. This page explains how it loads, draws and acts on history. For the user side, see History and Log.

Why we need it

People want to scroll the history, see where branches split and merged, read one commit, and act on it. Histories can be huge, so the Log loads history in pages, lays out the graph page by page, and only renders the rows you can see.

How it works

LogView.svelte fills the main area. The Log button in the activity bar, the empty main area, Shift+Cmd+L, View > Log and the X at the right end of the Log toolbar all call changesSelection.toggleLog(), which remembers the view you came from, so a second click returns you there. Git > Show Git Log (Cmd+9) and a repository row's ... > Show Log call showLog(repoRoot?) in views/gitActions.ts, which makes the repository active first and only opens the Log, never hides it.

Double-clicking a commit opens it in its own editor tab instead; see How commit tabs work.

Loading a page goes through the usual bridge:

sequenceDiagram
    participant LV as LogView
    participant API as api.ts
    participant CMD as history.rs
    participant LOG as git/log.rs
    LV->>API: getLog(repoPath, offset, 300, allRefs)
    API->>CMD: invoke get_log
    CMD->>LOG: page(repo, offset, limit capped at 1000, allRefs)
    LOG->>LOG: revwalk, topological and time order
    LOG-->>LV: CommitSummary list with ref labels
    LV->>LV: GraphBuilder.push(page), append rows

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log::page walks from HEAD with git2. When allRefs is set (the logAllRefs setting, on by default) it also pushes every local and remote branch, like git log --branches --remotes (tags and stashes are not walked). Each CommitSummary carries its parents and its ref labels.

GraphBuilder in src/lib/log/graph.ts gives each commit a lane. It keeps its lane state between calls, so page after page gives the same picture as the whole history at once. Rows store edges as flat number quadruples, and the UI library's CommitGraph draws them, with lane colors from ui/design-tokens/palette.json.

flowchart TD
    A["Scroll or open the Log"] --> B{"Near the end of loaded rows?"}
    B -->|"no"| C["Render only the visible rows plus overscan"]
    B -->|"yes, and more exist"| D["loadMore: getLog at offset = loaded count"]
    D --> E["GraphBuilder continues the lanes"]
    E --> F["Bump version so derived lists update"]
    F --> C

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A few details keep it fast:

• Plain arrays, not runes. commits, rows and indexById live outside $state, so commits are never wrapped in proxies; a version counter tells derived values they changed.
• Virtual list. Rows are a fixed 26 px; only the visible range plus 12 rows is rendered, and within 80 rows of the end the next 300 commits load.
• Reloads keep your place. When repoStore.historyVersion changes, the Log refetches as many commits as it had (up to 3000) and keeps the selection.
• Stale answers are dropped through a generation number captured by every load.

The filter searches loaded commits only (hash prefix, summary, author), and the graph collapses to one lane while filtering. Automatic paging pauses while filtering; a Load more button searches deeper. CommitDetails.svelte calls getCommitDetails (files per parent; see How merge commits work) and getCommitFileDiff.

Jumping to a commit from elsewhere

Blame and Back/Forward reach repoStore.showCommit(repoRoot, commitId, filePath, line, lineText). It switches the active repository if needed and sets repoStore.logFocus with a fresh token. An effect in LogView runs focusCommit, which loads pages until the commit appears (at most 20), centers it, and passes the line to CommitDetails, where revealLine uses findLine (src/lib/log/lineMatch.ts). If the commit is not found, a toast says so, and suggests all branches when logAllRefs is off.

Acting on a commit

The context menu's items write through repoStore.run or runOp with the git CLI (cherry-pick, revert --no-edit, reset, switch --detach); cherry-pick and revert return an OpOutcome, so conflicts are a normal result. They and Interactively Rebase from Here are disabled on merge commits; the rebase also needs a branch and hands over to startInteractiveRebase (How Interactive Rebase Works).

Reset offers Soft, Mixed, Hard and Keep; Hard asks twice. run_reset in commands/history.rs maps them to --soft, --mixed, --hard and --keep, refuses a revision that starts with -, and ends the arguments with -- so a revision named like a file is never read as a path. The Git menu's Reset HEAD dialog uses the same command.

An effect publishes the selected commit to logSelection.current (src/lib/log/logSelection.svelte.ts), and clears it when the Log closes. The Git menu reads it for Create Patch from Commit and Interactive Rebase.

Where the code lives

File	What it does
src/lib/views/LogView.svelte	Toolbar, filter, selection, blame focus, details split
src/lib/log/logHistory.svelte.ts	LogHistory: pages, reloads, find
src/lib/log/LogTable.svelte	Rows, on the library's DataTable
src/lib/log/logFilter.ts, commitMenu.ts	Filter and counts; right-click menu
src/lib/log/graph.ts	GraphBuilder: incremental lane layout
ui/web/src/lib/components/CommitGraph.svelte, logic/graphModel.ts	Draws one row of the graph (UI library)
src/lib/log/CommitDetails.svelte, commitLoader.svelte.ts	Commit message, changed files and per-file diff, revealLine
src/lib/log/lineMatch.ts	findLine: which diff line to scroll to
src/lib/log/format.ts	Dates and ref label sorting
src/lib/log/logSelection.svelte.ts	The selected commit, for Git menu items
src/lib/views/changes/selection.svelte.ts	toggleLog() and shownView
src/lib/stores/repo.svelte.ts	showCommit, logFocus, historyVersion
src-tauri/src/commands/history.rs	get_log, get_commit_details, get_commit_file_diff, cherry_pick, revert_commit, reset_to (run_reset), checkout_commit
src-tauri/src/git/log.rs	git2 revwalk, ref labels, commit details

Design decisions

Page the history and lay out the graph incrementally. Loading the whole history first would be slow and heavy on big repositories. The lane state carried between pages gives the same graph without redoing earlier pages. The backend is simpler: each page walks again from the tips and skips offset commits, so deep pages cost more.

Keep commit data outside Svelte runes. Proxies on tens of thousands of objects cost memory and time; one version counter is cheap, but every change must bump it (LogHistory does).

Filter only what is loaded. Filtering loaded commits is instant, and the label says "of N loaded commits" so nobody is misled.

Bugs we fixed

The Log could not be hidden.

• The issue: the Log was a permanent tab in the header, next to a Diff tab, and could not be hidden.
• Why it happened: the header treated the Log as one of several permanent tabs.
• The fix and why we chose it: at the user's request the Log became an activity bar toggle. toggleLog() remembers the previous view, so hiding the Log returns you where you were.

A type check failure in focusCommit.

• The issue: bun run check failed while diff steps were added to Back/Forward.
• Why it happened: a new token parameter clashed with the local load generation token.
• The fix and why we chose it: renaming the parameter kept the generation check untouched.

Tests

• src/lib/log/graph.test.ts: linear history, merges, lane reuse, octopus merges, several roots, duplicate parents, paging equals all-at-once, rows stay within their width.
• src-tauri/src/git/tests.rs: log_page_orders_newest_first_and_pages, log_page_in_unborn_repo_is_empty, log_page_labels_refs_and_includes_all_refs, log_details_lists_files_with_rename, diff_commit_file_sides.
• src-tauri/src/commands/tests.rs: cherry_pick_conflict_then_continue, revert_conflict_then_continue, reset_and_checkout_commit.
• src-tauri/src/commands/history.rs: reset_keep_moves_the_branch_and_keeps_local_changes, which also checks that an option-like revision and an unknown mode are refused.
• src/lib/log/logFilter.test.ts: matching, counts, the +N chip.
• src/lib/log/lineMatch.test.ts: findLine keeps or moves the line, ties, no match, CRLF.

Graph changes need a case in graph.test.ts; history command changes need a Rust test on a real repository from test_support.rs.

Keeping this page in sync

• Update this page when LogView.svelte, logHistory.svelte.ts, graph.ts, git/log.rs or commands/history.rs change behavior, page size or menu items.
• Update History and Log for any visible change.
• Retake log-graph.png, commit-details.png and log-context-menu.png when the Log looks different.
• See also How Blame Works, How Navigation Works and Frontend.