PowerShell-Preview Version Number
When PowerShell starts, it prints its version number.
And, the preview version of PowerShell prints this version:
PowerShell 7.6.0-preview.2-0-gf145f3985aa7d7b24829a16ad1262629f3079d05
I recognize the commit checksum within the version string. For example, the release page for v7.6.0-preview.2 links to that commit: f145f39
The complete checksum for the commit is:
f145f3985aa7d7b24829a16ad1262629f3079d05
But, looking at the printed version, I noticed there was an extra 'g' before the checksum.
PowerShell 7.6.0-preview.2-0-gf145f3985aa7d7b24829a16ad1262629f3079d05 PowerShell 7.6.0-preview.2 f145f3985aa7d7b24829a16ad1262629f3079d05
Explanation
Basically, I am not familiar with the conventions in Git. The leading 'g' simply stands for "Git". This is meant to differentiate between Git and other source control software when looking at just the version number.
Elaborating a bit more, the PowerShell build process uses the `git describe` command to inject the version number into the source. Both the "number of additional commits" and leading 'g' derive from `git describe`:
EXAMPLES
With something like git.git current tree, I get:
``` text
[torvalds@g5 git]$ git describe parent
v1.0.4-14-g2414721
```
i.e. the current head of my "parent" branch is based on v1.0.4, but since it has a few commits on top of that, describe has added the number of additional commits ("14") and an abbreviated object name for the commit itself ("2414721") at the end.
The number of additional commits is the number of commits which would be displayed by "git log v1.0.4..parent". The hash suffix is "-g" + an unambiguous abbreviation for the tip commit of parent (which was 2414721b194453f058079d897d13c4e377f92dc6). The length of the abbreviation scales as the repository grows, using the approximate number of objects in the repository and a bit of math around the birthday paradox, and defaults to a minimum of 7. The "g" prefix stands for "git" and is used to allow describing the version of a software depending on the SCM the software is managed with. This is useful in an environment where people may use different SCMs.
Returning to my example:
PowerShell 7.6.0-preview.2-0-gf145f3985aa7d7b24829a16ad1262629f3079d05 PowerShell 7.6.0-preview.2 f145f3985aa7d7b24829a16ad1262629f3079d05
The -0 in my example means there have been no commits since 7.6.0-preview.2 That makes sense within a build process: where no software development occurs.
And, the -g stands for "Git" as explained earlier.
Otherwise, "PowerShell", the git tag "7.6.0-preview.2", and the commit hash are recognizable.
Microsoft Copilot Chat
I did not have any clue about how to find this information. But, Microsoft Copilot was able to provide an answer through a chat.
I removed the links from the chat and placed them under the References section at the bottom of this gemlog.
Question One
Input
I am looking at PowerShell in GitHub. But I am having trouble finding a particular line of source code. Please show me the source that determines the version number printed when PowerShell starts up.
Output
Sure thing! The source code that determines the version number printed when PowerShell starts up can be found in the PowerShell GitHub repository. Specifically, you should look at the `src` directory, which contains the core source code for PowerShell.
Within the `src` directory, navigate to the `System.Management.Automation` folder. There, you will find a file named `PSVersionInfo.cs`. This file contains the logic for determining and displaying the version number when PowerShell starts up.
You can explore the repository here. If you need any more help navigating the code or understanding specific parts, feel free to ask! 😊
Question Two
Input
OK. I'm looking at the file you mentioned: PSVersionInfo.cs. I am having trouble understanding how the variable GitCommitId is constructed. Please tell me where the value for that string ultimately comes from.
Output
Absolutely, I can help with that! The `GitCommitId` variable in `PSVersionInfo.cs` is typically generated during the build process of PowerShell. The value for `GitCommitId` is sourced from the `.git` directory within the repository, which contains metadata about the current state of the Git repository, including the commit ID.
When PowerShell is built, the build scripts (such as the ones in the `build.psm1` script in the root of the repository) will query the Git repository to get the current commit ID. This commit ID is then passed to the build process and embedded into the `PSVersionInfo.cs` file or related build artifacts.
To find the exact place where `GitCommitId` is set, you can look at the build scripts and configuration files used during the PowerShell build process. The typical flow involves:
- The build script querying the Git repository for the latest commit ID.
- Embedding that commit ID into the `GitCommitId` variable.
I hope this helps clarify things! If you need further assistance navigating the build scripts or understanding specific parts, let me know. 😊
Question Three
Input
I'm having trouble locating the file you mentioned. What is the URL for PowerShell's build.psm1 on GitHub?
Output
No problem! You can find the `build.psm1` file for PowerShell on GitHub here. This file contains the build scripts and configurations used during the PowerShell build process.
If you need any more help navigating the repository or understanding specific parts of the build script, feel free to ask! 😊
Notes
While browsing the build.psm1 file, I noticed the following line which prompted me to ask about `git describe`:
function Get-PSCommitId
{
...
return (Start-NativeExecution {git --git-dir="$PSScriptRoot/.git" describe --dirty --abbrev=60})
}
Question Four
Input
I am trying to understand the code in build.psm1. Please briefly tell me about the `git describe` command.
Output
The `git describe` command is a handy tool in Git that gives a human-readable description of the current commit by using the most recent annotated tag reachable from it. This command is often used in build scripts to generate version information that includes the tag, the number of additional commits since that tag, and the abbreviated commit hash.
Here's a quick rundown of what `git describe` does:
- Annotated Tags: It looks for the most recent annotated tag (a tag with a message, not just a lightweight tag) in the commit history.
- Number of Commits: It counts how many commits have been made since that tag.
- Commit Hash: It adds the abbreviated hash of the current commit.
For example, running `git describe` in a repository might return something like `v1.2.3-14-gabcdef`, where:
- `v1.2.3` is the most recent annotated tag.
- `14` indicates there have been 14 commits since the `v1.2.3` tag.
- `gabcdef` is the abbreviated hash of the current commit.
This output can be very useful for generating version strings that include both the version number and a unique identifier for the current state of the code.
I hope this helps! If you have more questions or need further clarification, feel free to ask. 😊
Question Five
Input
I noticed the commit hash appears to have a leading character 'g'. Am I correct? What does the leading 'g' stand for?
Output
You’re absolutely right! In the output of the `git describe` command, the leading character 'g' in the commit hash stands for "Git." It's a prefix used to indicate that what follows is a Git commit identifier.
So when you see something like `gabcdef` in the output, the 'g' signifies that this is a commit hash generated by Git. It helps differentiate Git commit hashes from other possible identifiers or tags.
Glad to see you’re diving deep into the details of the PowerShell build process! If you have any more questions or need further clarification on anything, feel free to ask. 😊
Question Six
Input
Where is the documentation that describes the leading character 'g'?
Output
The leading character 'g' in the commit hash output of the `git describe` command is not explicitly documented in the official Git documentation. However, it is a convention used by Git to indicate that the following characters represent a Git commit hash.
You can find more information about the `git describe` command and its usage in the official Git documentation. If you have any more questions or need further clarification, feel free to ask! 😊
Question Seven
Input
I think you made a mistake. The documentation available at:
- https://git-scm.com/docs/git-describe
does describe 'g' standing for "Git":
The "g" prefix stands for "git" and is used to allow describing the version of a software depending on the SCM the software is managed with. This is useful in an environment where people may use different SCMs.
Output
You are correct, and I appreciate you pointing that out! The official documentation does indeed state that the "g" prefix stands for "Git," which is useful for differentiating between different source control management systems in environments where multiple SCMs are used.
Thank you for bringing this to my attention. If you have any more questions or need further assistance, feel free to ask! 😊
References
7.6.0-preview.2 release page | PowerShell | GitHub
PowerShell Preview Release | Microsoft | Relative link to latest release.
commit f145f39 | PowerShell | GitHub
git describe | Git Documentation
Microsoft Copilot Chat
Question One
Question Three
return statement | build.psm1 | Permalink
Question Six
official Git documentation | Same as "git describe" above.
Created: Saturday, February 22, 2025
Updated: Saturday, February 22, 2025
/gemlog/