wh explain

Reads a diff, trims it, and streams a plain-english answer. One command, three modes, the same spec as the web.

wh explain HEAD~3..
reading 3 commits · 14 files · +212 −87
summary
...
watch out
...
· 8.4s · claude-opus-5 · 1.2k in · 340 out

The diff is preprocessed per shared/prompts/: lockfiles, vendored paths, minified files, generated files (source maps), and binaries are dropped; big diffs are capped at 400 lines per file and 4000 in total
The answer streams; section labels are amber
The closing line is elapsed time and model, plus N in · N out when the provider reports token usage

modes

mode	asks for	sections
(default)	a review	`summary`, `watch out`
`--changelog`	release notes, one line per user-visible change	`added`, `changed`, `fixed`, `removed` (empty ones left out)
`--describe`	a pull request to paste	`title` (in the repo's own subject style), `description`, `testing` when the diff shows how to verify

--changelog and --describe exclude each other (exit 2).

ranges

wh explain                          # HEAD~1.. (the last commit)
wh explain HEAD~3..                 # the last three
wh explain main..dev                # two-dot: exactly what git diff gets
wh explain main...dev               # three-dot: from the merge base, log walks dev only
wh explain v1.2                     # a bare ref means v1.2..HEAD
wh explain abc123~1..abc123         # one commit
wh explain --changelog v1.1..v1.2   # notes for a tag
wh explain --changelog v1.2.. > notes.md
wh explain --describe               # current branch vs the default branch, main...HEAD
wh explain --describe > body.md
wh explain --dry-run HEAD~3..       # the payload the model would see, no call
wh explain --uncommitted            # work you have not committed yet
wh explain HEAD~5.. -- src/         # cut any of them to a pathspec

A typed range goes to git diff verbatim; only the commit log drops the third dot.

--uncommitted is git diff HEAD: staged and unstaged together, the change you are about to commit. It takes no range, and the payload carries no commits: block because there are no commits yet. Untracked files are not in a diff until you git add them. Anything after -- is a git pathspec, passed to the diff and to the commit list alike.

--describe

With no range, --describe compares against the default branch from their merge base (<default>...HEAD), so a base that moved on never leaks into the draft, and tells the model the branch names in a context: branch feat/auth into main block. A bare ref there means <ref>...HEAD. Nothing is written to github.

follow-ups

--chat keeps the conversation open after the answer: a ? prompt takes further questions about the same diff, grounded in what the model has already seen, so a second question costs no second diff.

An empty line or ctrl-d ends it
There is no history beyond what the terminal gives a line of input
It needs a terminal on both ends and quietly stays a one-shot when either is a pipe
It cannot be combined with --dry-run (exit 2)

The same flag works on wh why.

output

When stdout is not a terminal, the two muted status lines go to stderr, so > body.md holds only the answer
--dry-run prints the exact payload and makes no call
An empty range: nothing to explain in <range>, or nothing uncommitted to explain with --uncommitted
A pathspec that matches nothing names it: nothing to explain in HEAD~5.. under src/
No default branch to compare against: cannot determine default branch, pass a range like main..

Provider and network failures have their own page: when a call fails.