git bisect run for automated bisect - Step-by-Step Execution

Process Flow - git bisect run for automated bisect

Start git bisect

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Mark bad commit

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Mark good commit

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Git picks midpoint commit

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Run test script automatically

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Script returns 0 (good) or non-0 (bad)

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Git marks commit good/bad based on script

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Repeat until first bad commit found

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Bisect ends with culprit commit

This flow shows how git bisect uses an automated test script to find the first bad commit by repeatedly testing midpoint commits.

Execution Sample

Git

git bisect start
git bisect bad
git bisect good v1.0
git bisect run ./test_script.sh

This sequence starts bisect, marks bad and good commits, then runs an automated test script to find the bad commit.

Process Table

Step	Commit Tested	Test Script Result	Git Marks	Next Action
1	commit_8f3a	0 (good)	good	Test midpoint commit_4b2c
2	commit_4b2c	1 (bad)	bad	Test midpoint commit_6d7e
3	commit_6d7e	1 (bad)	bad	Test midpoint commit_7a9f
4	commit_7a9f	0 (good)	good	Test midpoint commit_6f1b
5	commit_6f1b	1 (bad)	bad	Bisect complete
6	-	-	-	First bad commit is commit_6f1b

💡 Bisect ends when only one bad commit remains between good and bad marks.

Status Tracker

Variable	Start	After 1	After 2	After 3	After 4	After 5	Final
Current Commit	none	commit_8f3a	commit_4b2c	commit_6d7e	commit_7a9f	commit_6f1b	commit_6f1b
Test Result	none	0	1	1	0	1	1
Good Commits	v1.0	v1.0, commit_8f3a	v1.0, commit_8f3a	v1.0, commit_8f3a	v1.0, commit_8f3a, commit_7a9f	v1.0, commit_8f3a, commit_7a9f	v1.0, commit_8f3a, commit_7a9f
Bad Commits	HEAD	HEAD	HEAD, commit_4b2c	HEAD, commit_4b2c, commit_6d7e	HEAD, commit_4b2c, commit_6d7e	HEAD, commit_4b2c, commit_6d7e, commit_6f1b	HEAD, commit_4b2c, commit_6d7e, commit_6f1b

Key Moments - 3 Insights

Why does git bisect test the midpoint commit instead of testing commits sequentially?

Git bisect uses a binary search approach to quickly narrow down the first bad commit by testing the midpoint between known good and bad commits, as shown in steps 1-5 of the execution_table.

What does the test script's exit code mean during 'git bisect run'?

The test script returns 0 if the commit is good and non-zero if bad. Git uses this to mark commits accordingly, as seen in the 'Test Script Result' column of the execution_table.

How does git bisect know when to stop testing commits?

Git bisect stops when it narrows down to the first bad commit between good and bad marks, indicated in the last row of the execution_table where bisect completes.

Visual Quiz - 3 Questions

Look at the execution_table at Step 3, what was the test script result for commit_6d7e?

A 0 (good)

B Script did not run

C 1 (bad)

D Unknown

💡 Hint

Check the 'Test Script Result' column for Step 3 in the execution_table.

At which step does git bisect mark commit_7a9f as good?

A Step 2

B Step 4

C Step 5

D Step 1

💡 Hint

Look at the 'Git Marks' column in the execution_table for commit_7a9f.

If the test script returned 0 for commit_6f1b instead of 1, what would happen next?

A Git would mark commit_6f1b as good and continue bisecting

B Git would mark commit_6f1b as bad and stop bisecting

C Git would stop bisecting immediately

D Git would ignore the result and test another commit

💡 Hint

Refer to how git marks commits based on test script results in the execution_table.

Concept Snapshot

git bisect run automates finding a bad commit by running a test script.
Start bisect with 'git bisect start', mark bad and good commits.
Use 'git bisect run <script>' to test commits automatically.
Script exit code 0 means good, non-zero means bad.
Git bisect uses binary search to find the first bad commit quickly.

Full Transcript

Git bisect run automates the process of finding the first bad commit by running a test script on each commit. The process starts by marking a known bad commit and a known good commit. Git then tests the midpoint commit by running the script. If the script returns 0, the commit is marked good; if non-zero, it is marked bad. Git repeats this binary search until it finds the first bad commit. This method speeds up debugging by automating testing and narrowing down the culprit commit efficiently.