take a look at the flake's sourceInfo attrset;

The commit hash is available as either rev and shortRev if the repo is clean, or dirtyRev and dirtyShortRev when the repo is dirty. In practice you'll want to access it as sourceInfo.rev or sourceInfo.dirtyRev.

As for the overall hash that should be affected even when dirty: there's sourceInfo.narHash.

You might find it interesting to inspect the available attrs in the repl:

$ nix repl
Nix 2.28.1
Type :? for help.

nix-repl> :lf .
Added 29 variables.

nix-repl> :p sourceInfo
{
  lastModified = 1742921445;
  lastModifiedDate = "20250325165045";
  narHash = "sha256-ACj6k+YN217sS5+UpDeu+pN1HIjDSxASeVgCRcF36ic=";
  outPath = "/nix/store/38i7dj4q0hdd2z0byar8vq9is3ifhvdn-source";
  rev = "87579c987a86ccd6992e847dd95fb4f0e95809d5";
  revCount = 3020;
  shortRev = "87579c9";
  submodules = false;
}

$ touch test && git add test

$ nix repl

Nix 2.28.1
Type :? for help.

nix-repl> :lf .
warning: Git tree '/home/matt/nixvim/pr' is dirty
Added 28 variables.

nix-repl> :p sourceInfo
{
  dirtyRev = "87579c987a86ccd6992e847dd95fb4f0e95809d5-dirty";
  dirtyShortRev = "87579c9-dirty";
  lastModified = 1742921445;
  lastModifiedDate = "20250325165045";
  narHash = "sha256-mdW66khbVmSx62kWDW/FwAMEUCQs9sKyS6zAGBXKj0U=";
  outPath = "/nix/store/hw7jgd4q25kg83jnnb7c90mw360d38fl-source";
  submodules = false;
}

take a look at the flake's sourceInfo attrset;

The commit hash is available as either rev and shortRev if the repo is clean, or dirtyRev and dirtyShortRev when the repo is dirty. In practice you'll want to access it as sourceInfo.rev or sourceInfo.dirtyRev.

As for the overall hash that should be affected even when dirty: there's sourceInfo.narHash.

You might find it interesting to inspect the available attrs in the repl:

$ nix repl
Nix 2.28.1
Type :? for help.

nix-repl> :lf .
Added 29 variables.

nix-repl> :p sourceInfo
{
  lastModified = 1742921445;
  lastModifiedDate = "20250325165045";
  narHash = "sha256-ACj6k+YN217sS5+UpDeu+pN1HIjDSxASeVgCRcF36ic=";
  outPath = "/nix/store/38i7dj4q0hdd2z0byar8vq9is3ifhvdn-source";
  rev = "87579c987a86ccd6992e847dd95fb4f0e95809d5";
  revCount = 3020;
  shortRev = "87579c9";
  submodules = false;
}

$ touch test && git add test

$ nix repl

Nix 2.28.1
Type :? for help.

nix-repl> :lf .
warning: Git tree '/home/matt/nixvim/pr' is dirty
Added 28 variables.

nix-repl> :p sourceInfo
{
  dirtyRev = "87579c987a86ccd6992e847dd95fb4f0e95809d5-dirty";
  dirtyShortRev = "87579c9-dirty";
  lastModified = 1742921445;
  lastModifiedDate = "20250325165045";
  narHash = "sha256-mdW66khbVmSx62kWDW/FwAMEUCQs9sKyS6zAGBXKj0U=";
  outPath = "/nix/store/hw7jgd4q25kg83jnnb7c90mw360d38fl-source";
  submodules = false;
}

Within your flake, these are accessed via the special self input.

outputs =
  {self, ...}@inputs:
  let
    # here you can access most attrs in sourceInfo directly from self
    # or alternatively, access self.sourceInfo explicitly
    foo = self.narHash;
    bar = self.sourceInfo.narHash;
  in
  builtins.trace self.sourceInfo
  { };

take a look at the flake's sourceInfo attrset;

The commit hash is available as either rev and shortRev if the repo is clean, or dirtyRev and dirtyShortRev when the repo is dirty. In practice you'll want to access it as sourceInfo.rev or sourceInfo.dirtyRev.

As for the overall hash that should be affected even when dirty: there's sourceInfo.narHash.

You might find it interesting to inspect the available attrs in the repl:

$ nix repl
Nix 2.28.1
Type :? for help.

nix-repl> :lf .
Added 29 variables.

nix-repl> :p sourceInfo
{
  lastModified = 1742921445;
  lastModifiedDate = "20250325165045";
  narHash = "sha256-ACj6k+YN217sS5+UpDeu+pN1HIjDSxASeVgCRcF36ic=";
  outPath = "/nix/store/38i7dj4q0hdd2z0byar8vq9is3ifhvdn-source";
  rev = "87579c987a86ccd6992e847dd95fb4f0e95809d5";
  revCount = 3020;
  shortRev = "87579c9";
  submodules = false;
}

$ touch test && git add test

$ nix repl

Nix 2.28.1
Type :? for help.

nix-repl> :lf .
warning: Git tree '/home/matt/nixvim/pr' is dirty
Added 28 variables.

nix-repl> :p sourceInfo
{
  dirtyRev = "87579c987a86ccd6992e847dd95fb4f0e95809d5-dirty";
  dirtyShortRev = "87579c9-dirty";
  lastModified = 1742921445;
  lastModifiedDate = "20250325165045";
  narHash = "sha256-mdW66khbVmSx62kWDW/FwAMEUCQs9sKyS6zAGBXKj0U=";
  outPath = "/nix/store/hw7jgd4q25kg83jnnb7c90mw360d38fl-source";
  submodules = false;
}

Within your flake, these are accessed via the special self input, which represents the fully evaluated flake.

outputs =
  {self, ...}@inputs:
  let
    # here you can access most attrs in sourceInfo directly from self
    # or alternatively, access self.sourceInfo explicitly
    foo = self.narHash;
    bar = self.sourceInfo.narHash;
  in
  builtins.trace self.sourceInfo
  { };