fix: fix blob command based on spec

[ghost]

This PR fixes blob command based on updated spec.

Resolves #1171

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 76.91%. Comparing base (73a4da6) to head (71736e9).
Report is 1 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1242      +/-   ##
==========================================
+ Coverage   76.81%   76.91%   +0.09%     
==========================================
  Files          68       68              
  Lines        3809     3825      +16     
==========================================
+ Hits         2926     2942      +16     
  Misses        680      680              
  Partials      203      203              

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[Copilot]

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[Copilot]

Pull Request Overview

This PR fixes the blob sign command to meet the updated spec and improves the handling of signature file paths and error cases across sign, verify, and inspect commands. Key changes include:

• Removing the use of WithWorkDir in favor of dynamically computing the blob’s directory and signature file path.
• Adding new test cases for failure scenarios (e.g. empty blob path or empty signature directory).
• Refining command flag behavior and help messages to reflect the new default behavior of storing signature files in the same directory as the blob.

Reviewed Changes

Copilot reviewed 11 out of 16 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
test/e2e/suite/command/blob/sign.go	Updates test cases to compute blob directory dynamically and update expected output strings.
test/e2e/suite/command/blob/verify.go	Removes WithWorkDir and uses blobDir consistently for signature file path construction.
cmd/notation/blob/sign.go	Updates help messages, adds pre-run validations, and defaults signature directory to blob location.
test/e2e/internal/notation/host.go	Replaces the global blob path with a dynamically created blob file via CreateBlobFile.
cmd/notation/blob/verify.go	Introduces a shorthand flag for the signature flag.
test/e2e/suite/command/blob/inspect.go	Uses signatureFilepath with blobDir for inspecting blob signatures.
cmd/notation/blob/sign_test.go	Adjusts test flags in accordance with the removal of an explicit signatureDirectory.
test/e2e/internal/notation/init.go	Removes the environment variable for blob path as it is now generated.

Files not reviewed (5)

• go.mod: Language not supported
• test/e2e/go.mod: Language not supported
• test/e2e/plugin/go.mod: Language not supported
• test/e2e/run.sh: Language not supported
• test/e2e/testdata/blob/blobFile.txt: Language not supported

Comments suppressed due to low confidence (2)

test/e2e/suite/command/blob/sign.go:31

• [nitpick] Consider using a more descriptive test case name that explicitly conveys the default behavior or scenario being validated instead of 'with default'.

It("with default", func() {

cmd/notation/blob/verify.go:89

• [nitpick] Ensure that the shorthand flag 's' is mentioned in the command help or documentation so that users are aware of its availability.

command.Flags().StringVarP(&opts.signaturePath, "signature", "s", "", "filepath of the signature to be verified")

[shizhMSFT]

LGTM

[JeyJeyGao]

LGTM