Git Diff Risk Analyzer

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A Git diff summary is a map of review surface before the full patch is opened. It reduces a change to paths, additions, deletions, and sometimes binary markers, which helps reviewers spot concentration, wide blast radius, and unusual removal patterns early. The summary cannot prove correctness, but it can show where attention should start.

Line count is only a rough proxy for risk. Ten lines in authentication, billing, migrations, infrastructure, permissions, or dependency files may deserve more scrutiny than hundreds of documentation or generated-output lines. A lockfile can be routine when it matches a deliberate dependency update; a tiny schema change can still need rollback planning, data compatibility review, and owner signoff.

Useful diff triage keeps a few signals separate. Churn is the total number of added and deleted lines. Path sensitivity reflects higher-consequence directories and filenames. Deletion pressure asks how much behavior or configuration is being removed. Generated artifacts should be checked against their source change, and binary changes need file-aware review because line-by-line evidence is unavailable.

Common Git diff review signals and why they matter
Review signal	Why it matters	Common mistake
High churn	More changed lines increase the surface area a reviewer must read and test.	Treating every large file as equally risky, including generated output that should be reviewed from its source.
Sensitive path	Changes in security, data, billing, infrastructure, or migration paths can affect more than the edited file.	Assuming a small diff is safe because the line count is low.
Deletion-heavy change	Removed code, configuration, or schema objects may need rollback planning and test evidence.	Reading deletions as simplification without checking behavior that depended on them.
Generated or lockfile change	The generated artifact should match the source change that produced it.	Reviewing the artifact by hand while missing the source or dependency cause.

Process diagram showing changed files moving through churn, path signals, and review routing.

Automated review triage is still weaker than human context. It can flag files that deserve owner review, wider test evidence, or source-artifact consistency checks, but it cannot decide whether the design is appropriate, whether tests prove the right behavior, or whether a product tradeoff is acceptable.

A practical review habit combines the summary with ownership and intent. Start with sensitive paths and heavy churn, confirm whether generated files match their sources, then read the actual patch with the right reviewer instead of letting raw line count decide confidence.

How to Use This Tool:

Paste a Git change summary, tune the review thresholds to your repository, and read the results as a routing checklist.

Paste Git diff stat text. git diff --numstat is the cleanest source because each line gives additions, deletions, and path. Common --stat pipe-bar lines and path-first numeric lines are also accepted.
Use Browse diff/TXT or drag a DIFF, PATCH, or TXT file when the summary is already saved. Files larger than 2 MiB are refused for browser-side analysis.
Fill Branch or PR with the change identifier you want to see in the summary and downloaded report data.
Set Change threshold to the changed-line count that should mark one file as large. The same number also marks a wide diff when the changed file count reaches it.
Adjust Risk path terms for the repository. Terms such as migration, schema, auth, payment, infra, and lock match file paths case-insensitively.
Open Advanced when deletion-heavy changes or generated artifacts need different policy. Deletion pressure sets the percent cutoff, and Generated or lockfile terms controls artifact matching.
Read File Risk Ledger for file-by-file scores, then Review Queue for the action list. Use Churn Weight Map when you need to see which files dominate additions and deletions.

If the results show no file rows, paste or load text that includes additions, deletions, and paths. The sample input is useful for comparing the expected shape before retrying your own diff summary.

Interpreting Results:

File Risk Ledger is the main evidence table. It lists each parsed path, the Delta, Change size, matched Risk signals, the score-derived Level, and a short Review note. A critical or high level means the file should be routed before merge, not that the change is automatically wrong.

Review Queue turns file scores and totals into review actions. High-risk files point to owner review, wide diffs suggest splitting the pull request or adding a subsystem checklist, deletion pressure asks for rollback and test evidence, and generated files ask for a source-artifact consistency check.

Git diff risk result bands and recommended checks
Level	Score boundary	What to do next
Critical	`score >= 70`	Require focused owner review before merge.
High	`45 <= score < 70`	Route the file to a domain reviewer.
Medium	`22 <= score < 45`	Review with the normal pull-request checklist.
Low	`score < 22`	Treat as a low change-risk signal, then still read the patch.

False confidence is the main risk. A low score can miss a subtle one-line bug, and a high score can be expected for a deliberate generated file or migration. Confirm the Risk signals, compare the Review Queue action with the pull-request intent, and read the actual patch before approving.

Technical Details:

Git exposes several compact diff summaries. Numstat is the most reliable machine-readable form because it records additions, deletions, and path as separate values. Stat-style output is more readable for humans, but additions and deletions must be estimated from plus and minus markers when the compact bar is the only available evidence.

The score combines review surface with path and content signals. Changed lines estimate how much text must be checked. Path terms represent areas where a small edit can have wider consequences. Deletion mix raises rollback attention, generated artifacts raise consistency checks, and binary rows receive a separate signal because text churn is unavailable.

Formula Core

Each parsed file receives a score from 0 to 100. The score is capped after all point contributions are added.

S = \min (100, round (\frac{C}{T} \times 25) + 22 R + 18 D + 8 G + 10 B)

Git diff risk score variables
Symbol	Meaning	Source or boundary
`S`	Final file score.	Rounded and capped at `100`.
`C`	Changed lines.	Additions plus deletions for the file.
`T`	Change threshold.	At least `1`; default is `12`.
`R`	Number of matched risk path terms.	Case-insensitive substring matches against the path.
`D`	Deletion-heavy flag.	`1` when deletion percentage is greater than or equal to the configured deletion pressure.
`G`	Generated or lockfile flag.	`1` when a generated-artifact term matches the path.
`B`	Binary diff flag.	`1` when additions or deletions are unavailable in numstat form.

Rule Core

Risk signals are additive, so a file can become critical through one very large churn value, several path matches, or a combination of moderate churn and sensitive-path signals.

Git diff risk score components and boundaries
Component	Point contribution	Boundary behavior
Churn	`round((changed lines / change threshold) * 25)`.	A file at or above the threshold receives at least `25` churn points before other signals.
Risk path	`22` points for each matched term.	Matching is case-insensitive and can match any substring in the path.
Deletion mix	`18` points.	Applies when deletions divided by changed lines is `>=` the deletion pressure percentage.
Generated or lockfile	`8` points.	Applies when the path contains a configured generated-artifact term.
Binary diff	`10` points.	Applies when numstat reports `-` instead of numeric additions or deletions.

For example, src/payment/retry.js with 42 additions and 8 deletions has 50 changed lines. With a threshold of 12, one matched payment risk term, and deletion pressure set to 35%, the churn contribution is round((50 / 12) * 25) = 104, plus 22 path points, then the final score is capped at 100. The file lands in the critical band.

Accepted Git diff summary row shapes
Input shape	Example	How it is read
Numstat	`42 8 src/payment/retry.js`	Additions, deletions, and path are read directly.
Path-first numeric	`src/payment/retry.js 42 8`	The path is read first, followed by additions and deletions.
Stat bar	`src/app.js \| 20 +++++---`	Total changed lines come from the number, while plus and minus markers estimate the split.
Binary numstat	`- - assets/logo.png`	The file is flagged as binary and line churn is treated as unavailable.

The churn chart uses the ten largest files by changed lines and stacks additions with deletions. It helps spot concentration, but it cannot show semantic complexity, dependency behavior, deleted test meaning, or whether a generated file was produced from the intended source change.

Privacy Notes:

Pasted diff summaries and browsed files are parsed in the browser. Downloaded or copied reports can still reveal branch names, file paths, unreleased features, and sensitive repository areas, so share them only with the intended reviewers.

Worked Examples:

Payment retry review: A diff summary with 42 8 src/payment/retry.js and the default payment risk term produces a critical Level in File Risk Ledger. The Review note should push the file to a payment-domain reviewer before merge.

Wide documentation and code mix: Twelve changed files at a threshold of 12 create a Wide diff item in Review Queue. If most files are documentation but one path matches auth, review the authentication file first and decide whether the remaining files can stay in the same pull request.

Deletion-heavy migration: A migration folder row with 5 additions and 20 deletions has an 80% deletion mix. With Deletion pressure at 35%, the ledger marks deletion-heavy and the queue asks for data, migration, and rollback coverage checks.

No rows after paste: A pasted full patch hunk may leave File Risk Ledger empty because the input does not contain summary rows with additions, deletions, and paths. Regenerate the source with git diff --numstat or load the sample to compare the expected shape.

Advanced Tips:

Use git diff --numstat when you can. It gives the clearest additions, deletions, and path columns, and it marks binary rows with dashes instead of pretending they have line counts. Use git diff --stat when a human-readable summary is all you have, but treat its plus and minus bar as an estimate.

Calibrate Change threshold to the repository, not to a universal rule. A service with many generated files may need a higher threshold to avoid noisy large-file signals, while a security-sensitive library may need a lower threshold so concentrated edits surface earlier.

Keep Risk path terms short and repository-specific. Terms such as auth, payment, schema, and migration are useful when they match real ownership or rollback concerns. Overly broad terms can make normal files look urgent and weaken the review queue.

Review generated files by cause. A lockfile, minified file, or generated directory should usually be checked against the dependency change, build command, or source artifact that produced it. The file may score high because the review method is different, not because the generated output should be hand-edited.

FAQ:

Should I paste a full patch?

No. Paste a diff summary such as git diff --numstat or common git diff --stat output. Full patch hunks do not provide the row shape needed for File Risk Ledger.

Why did a lockfile or generated file score higher?

Generated and lockfile paths receive a specific signal so reviewers check that the artifact matches the source, dependency, or build change that produced it. The score is not a request to hand-edit the generated file.

Can a low level still hide a serious bug?

Yes. Low means the configured churn, path, deletion, generated, and binary signals were light. A one-line behavior change in a sensitive subsystem can still need senior review.

Why does a binary file have no line count?

Numstat uses - when additions and deletions are unavailable for a binary diff. The row receives a binary signal, but the actual file should be inspected with an appropriate binary-aware review method.

What should I change when the queue feels too noisy?

Raise Change threshold for repositories with naturally large files, remove overly broad Risk path terms, or adjust Deletion pressure if ordinary cleanup commits are being treated as rollback-sensitive.

Glossary:

Numstat: A Git diff summary format that lists additions, deletions, and path for each changed file.
Diffstat: A compact changed-file summary, often shown with a file path, total line count, and plus or minus markers.
Churn: The total changed-line count for a file, calculated as additions plus deletions.
Path sensitivity: The review importance attached to file paths that touch high-consequence areas such as migrations, authentication, payments, infrastructure, or lockfiles.
Deletion pressure: The percentage of changed lines that are deletions, used to flag changes that may need rollback and behavior checks.
Generated artifact: A lockfile, generated file, or build output that should be checked against the source change that produced it.

References:

git-diff Documentation, Git SCM.
About Pull Request Reviews, GitHub Docs.
Reviewing Proposed Changes in a Pull Request, GitHub Docs.
About Code Owners, GitHub Docs.
How to compare two Git branches with diff, Simplified Guide.
How to Review a Commit with Codex, simplified.guide.