Add fish shell format for export-credentials

[minjcho]

Issue: #9670

Description of changes:

• Add a new output format, --format fish, to aws configure export-credentials.
• Fish shell does not support export VAR=value; it uses set -gx VAR value.

This change lets Fish users apply exported credentials directly without extra conversion.

Usage:

aws configure export-credentials --format fish | source

Example output:

set -gx AWS_ACCESS_KEY_ID AKIAIOSFODNN7EXAMPLE
set -gx AWS_SECRET_ACCESS_KEY wJalrXUtnFEMI/K7MDENG/bPxRfiCYEXAMPLEKEY
set -gx AWS_SESSION_TOKEN token
set -gx AWS_CREDENTIAL_EXPIRATION 2023-01-01T00:00:00Z

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[Copilot]

Pull request overview

This pull request adds Fish shell support to the aws configure export-credentials command, allowing Fish shell users to export AWS credentials in a format compatible with their shell.

Changes:

• Added a new FishShellFormatter class that outputs credentials using Fish shell's set -gx syntax
• Updated the SUPPORTED_FORMATS dictionary to include the new Fish formatter
• Added comprehensive unit tests for the Fish shell formatter covering both static and temporary credentials

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 2 comments.

File	Description
awscli/customizations/configure/exportcreds.py	Implements FishShellFormatter class and registers it in SUPPORTED_FORMATS
tests/unit/customizations/configure/test_exportcreds.py	Adds test cases for FishShellFormatter with expected output formats

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[Copilot]

The Fish shell formatter should quote the variable value to handle credentials that may contain special characters (spaces, quotes, etc.). Similar to PowerShell's approach, the format should be 'set -gx {var_name} "{var_value}"' to ensure values with spaces or special characters are properly handled. While AWS credential values rarely contain such characters, session tokens could potentially include them, and proper quoting ensures robustness.

Suggested change

	_VAR_FORMAT = 'set -gx {var_name} {var_value}'
	_VAR_FORMAT = 'set -gx {var_name} "{var_value}"'

[Copilot]

The expected test output should include quotes around the values to match the corrected Fish shell format. The format should be 'set -gx AWS_ACCESS_KEY_ID "access_key"' instead of 'set -gx AWS_ACCESS_KEY_ID access_key' to properly handle values with special characters.

Suggested change

	'set -gx AWS_ACCESS_KEY_ID access_key\n'
	'set -gx AWS_SECRET_ACCESS_KEY secret_key\n'
	),
	(
	'set -gx AWS_ACCESS_KEY_ID access_key\n'
	'set -gx AWS_SECRET_ACCESS_KEY secret_key\n'
	'set -gx AWS_SESSION_TOKEN token\n'
	'set -gx AWS_CREDENTIAL_EXPIRATION 2023-01-01T00:00:00Z\n'
	'set -gx AWS_ACCESS_KEY_ID "access_key"\n'
	'set -gx AWS_SECRET_ACCESS_KEY "secret_key"\n'
	),
	(
	'set -gx AWS_ACCESS_KEY_ID "access_key"\n'
	'set -gx AWS_SECRET_ACCESS_KEY "secret_key"\n'
	'set -gx AWS_SESSION_TOKEN "token"\n'
	'set -gx AWS_CREDENTIAL_EXPIRATION "2023-01-01T00:00:00Z"\n'